diff --git a/DESCRIPTION b/DESCRIPTION
index 629cf838..d8ca0105 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,14 +1,18 @@
 Package: RcppParallel
 Type: Package
 Title: Parallel Programming Tools for 'Rcpp'
-Version: 5.0.2-9000
+Version: 5.1.0-9000
 Authors@R: c(
     person("JJ", "Allaire", role = c("aut"), email = "jj@rstudio.com"),
     person("Romain", "Francois", role = c("aut", "cph")),
     person("Kevin", "Ushey", role = c("aut", "cre"), email = "kevin@rstudio.com"),
     person("Gregory", "Vandenbrouck", role = "aut"),
     person("Marcus", "Geelnard", role = c("aut", "cph"),
-       comment = "TinyThread library, http://tinythreadpp.bitsnbites.eu/"),
+       comment = "TinyThread library, https://tinythreadpp.bitsnbites.eu/"),
+    person("Hamada S.", "Badr",
+       email = "badr@jhu.edu",
+       role = c("ctb"),
+       comment = c(ORCID = "0000-0002-9808-2344")),
     person(family = "RStudio", role = "cph"),
     person(family = "Intel", role = c("aut", "cph"),
        comment = "Intel TBB library, https://www.threadingbuildingblocks.org/"),
@@ -24,12 +28,12 @@ Suggests:
     RUnit,
     knitr,
     rmarkdown
-SystemRequirements: GNU make, Windows: cmd.exe and cscript.exe, Solaris: g++ is required
+SystemRequirements: GNU make, Intel TBB, Windows: cmd.exe and cscript.exe, Solaris: g++ is required
 License: GPL (>= 2)
-URL: http://rcppcore.github.io/RcppParallel, https://github.com/RcppCore/RcppParallel
+URL: https://rcppcore.github.io/RcppParallel/, https://github.com/RcppCore/RcppParallel
 BugReports: https://github.com/RcppCore/RcppParallel/issues
 Biarch: TRUE
-Collate: 
+Collate:
    'build.R'
    'hooks.R'
    'options.R'
diff --git a/R/build.R b/R/build.R
index 95cbf5e8..33e393f4 100644
--- a/R/build.R
+++ b/R/build.R
@@ -41,13 +41,23 @@ inlineCxxPlugin <- function() {
 }
 
 tbbCxxFlags <- function() {
-   
+
    flags <- c()
-   
+
    # opt-in to TBB on Windows
    if (Sys.info()['sysname'] == "Windows")
       flags <- paste(flags, "-DRCPP_PARALLEL_USE_TBB=1")
-   
+
+   if (dir.exists(Sys.getenv("TBB_INC"))) {
+       TBB_INC <- asBuildPath(Sys.getenv("TBB_INC"))
+
+       if (file.exists(file.path(TBB_INC, "tbb", "version.h"))) {
+          flags <- paste0("-I", shQuote(TBB_INC), " -DTBB_INTERFACE_NEW")
+       } else {
+          flags <- paste0("-I", shQuote(TBB_INC))
+       }
+   }
+
    flags
 }
 
@@ -57,6 +67,9 @@ tbbLdFlags <- function() {
    if ((Sys.info()['sysname'] %in% c("Windows", "SunOS")) && !isSparc()) {
       tbb <- tbbLibPath()
       paste("-L", asBuildPath(dirname(tbb)), " -ltbb -ltbbmalloc", sep = "")
+   } else if (dir.exists(Sys.getenv("TBB_LIB"))) {
+      TBB_LIB <- asBuildPath(Sys.getenv("TBB_LIB"))
+      paste0("-L", shQuote(TBB_LIB), " -Wl,-rpath,", TBB_LIB, " -ltbb -ltbbmalloc")
    } else {
       ""
    }
@@ -66,19 +79,32 @@ tbbLdFlags <- function() {
 tbbLibPath <- function(suffix = "") {
    sysname <- Sys.info()['sysname']
    tbbSupported <- list(
-      "Darwin" = paste("libtbb", suffix, ".dylib", sep = ""), 
-      "Linux" = paste("libtbb", suffix, ".so.2", sep = ""), 
+      "Darwin" = paste("libtbb", suffix, ".dylib", sep = ""),
+      "Linux" = paste("libtbb", suffix, ".so.2", sep = ""),
       "Windows" = paste("tbb", suffix, ".dll", sep = ""),
       "SunOS" = paste("libtbb", suffix, ".so", sep = "")
    )
-   if ((sysname %in% names(tbbSupported)) && !isSparc()) {
-      libDir <- "lib/"
-      if (sysname == "Windows")
-         libDir <- paste(libDir, .Platform$r_arch, "/", sep="")
-      system.file(paste(libDir, tbbSupported[[sysname]], sep = ""), 
-                  package = "RcppParallel")
+
+   if (dir.exists(Sys.getenv("TBB_LIB"))) {
+      TBB_LIB <- asBuildPath(Sys.getenv("TBB_LIB"))
+      asBuildPath(file.path(TBB_LIB, paste("libtbb", suffix, ".so", sep = "")))
    } else {
-      NULL
+      if ((sysname %in% names(tbbSupported)) && !isSparc()) {
+         libDir <- "lib/"
+         if (sysname == "Windows")
+            libDir <- paste(libDir, .Platform$r_arch, "/", sep="")
+
+         tbb_path <- system.file(paste(libDir, tbbSupported[[sysname]], sep = ""),
+                                 package = "RcppParallel")
+         if (sysname == "Linux" && !file.exists(tbb_path)) {
+             system.file(paste(libDir, "libtbb", suffix, ".so", sep =""),
+                         package = "RcppParallel")
+         } else {
+            tbb_path
+         }
+      } else {
+         NULL
+      }
    }
 }
 
diff --git a/inst/NEWS b/inst/NEWS
index 20a22bb2..30566085 100644
--- a/inst/NEWS
+++ b/inst/NEWS
@@ -1,6 +1,13 @@
-RcppParallel 5.0.3 (UNRELEASED)
+RcppParallel 5.1.0 (UNRELEASED)
 ------------------------------------------------------------------------
 
+* Added support for external TBB library via TBB_INC and/or TBB_LIB environment variables.
+* Updated TBB functionality for the new interface.
+* Falling back to building TBB from local source code.
+* Backward TBB compatibility based on `__TBB_tbb_stddef_H`.
+* Resolved conflicts between system and local TBB headers.
+* Fixed URLs, used HTTPS, and minor cleanups.
+* Updated package DESCRIPTION and bumped version.
 * setThreadOptions(...) can again be called multiple times per session.
   The requested number of threads will be used for invocations to parallelFor()
   and parallelReduce() that don't explicitly request a specific number of threads.
diff --git a/inst/include/serial/tbb/parallel_for.h b/inst/include/tbb_local/serial/tbb/parallel_for.h
similarity index 100%
rename from inst/include/serial/tbb/parallel_for.h
rename to inst/include/tbb_local/serial/tbb/parallel_for.h
diff --git a/inst/include/serial/tbb/tbb_annotate.h b/inst/include/tbb_local/serial/tbb/tbb_annotate.h
similarity index 100%
rename from inst/include/serial/tbb/tbb_annotate.h
rename to inst/include/tbb_local/serial/tbb/tbb_annotate.h
diff --git a/inst/include/tbb/aggregator.h b/inst/include/tbb_local/tbb/aggregator.h
similarity index 100%
rename from inst/include/tbb/aggregator.h
rename to inst/include/tbb_local/tbb/aggregator.h
diff --git a/inst/include/tbb/aligned_space.h b/inst/include/tbb_local/tbb/aligned_space.h
similarity index 100%
rename from inst/include/tbb/aligned_space.h
rename to inst/include/tbb_local/tbb/aligned_space.h
diff --git a/inst/include/tbb/atomic.h b/inst/include/tbb_local/tbb/atomic.h
similarity index 100%
rename from inst/include/tbb/atomic.h
rename to inst/include/tbb_local/tbb/atomic.h
diff --git a/inst/include/tbb/blocked_range.h b/inst/include/tbb_local/tbb/blocked_range.h
similarity index 100%
rename from inst/include/tbb/blocked_range.h
rename to inst/include/tbb_local/tbb/blocked_range.h
diff --git a/inst/include/tbb/blocked_range2d.h b/inst/include/tbb_local/tbb/blocked_range2d.h
similarity index 100%
rename from inst/include/tbb/blocked_range2d.h
rename to inst/include/tbb_local/tbb/blocked_range2d.h
diff --git a/inst/include/tbb/blocked_range3d.h b/inst/include/tbb_local/tbb/blocked_range3d.h
similarity index 100%
rename from inst/include/tbb/blocked_range3d.h
rename to inst/include/tbb_local/tbb/blocked_range3d.h
diff --git a/inst/include/tbb/cache_aligned_allocator.h b/inst/include/tbb_local/tbb/cache_aligned_allocator.h
similarity index 100%
rename from inst/include/tbb/cache_aligned_allocator.h
rename to inst/include/tbb_local/tbb/cache_aligned_allocator.h
diff --git a/inst/include/tbb/combinable.h b/inst/include/tbb_local/tbb/combinable.h
similarity index 100%
rename from inst/include/tbb/combinable.h
rename to inst/include/tbb_local/tbb/combinable.h
diff --git a/inst/include/tbb/compat/condition_variable b/inst/include/tbb_local/tbb/compat/condition_variable
similarity index 100%
rename from inst/include/tbb/compat/condition_variable
rename to inst/include/tbb_local/tbb/compat/condition_variable
diff --git a/inst/include/tbb/compat/ppl.h b/inst/include/tbb_local/tbb/compat/ppl.h
similarity index 100%
rename from inst/include/tbb/compat/ppl.h
rename to inst/include/tbb_local/tbb/compat/ppl.h
diff --git a/inst/include/tbb/compat/thread b/inst/include/tbb_local/tbb/compat/thread
similarity index 100%
rename from inst/include/tbb/compat/thread
rename to inst/include/tbb_local/tbb/compat/thread
diff --git a/inst/include/tbb/compat/tuple b/inst/include/tbb_local/tbb/compat/tuple
similarity index 100%
rename from inst/include/tbb/compat/tuple
rename to inst/include/tbb_local/tbb/compat/tuple
diff --git a/inst/include/tbb/concurrent_hash_map.h b/inst/include/tbb_local/tbb/concurrent_hash_map.h
similarity index 100%
rename from inst/include/tbb/concurrent_hash_map.h
rename to inst/include/tbb_local/tbb/concurrent_hash_map.h
diff --git a/inst/include/tbb/concurrent_lru_cache.h b/inst/include/tbb_local/tbb/concurrent_lru_cache.h
similarity index 100%
rename from inst/include/tbb/concurrent_lru_cache.h
rename to inst/include/tbb_local/tbb/concurrent_lru_cache.h
diff --git a/inst/include/tbb/concurrent_priority_queue.h b/inst/include/tbb_local/tbb/concurrent_priority_queue.h
similarity index 100%
rename from inst/include/tbb/concurrent_priority_queue.h
rename to inst/include/tbb_local/tbb/concurrent_priority_queue.h
diff --git a/inst/include/tbb/concurrent_queue.h b/inst/include/tbb_local/tbb/concurrent_queue.h
similarity index 100%
rename from inst/include/tbb/concurrent_queue.h
rename to inst/include/tbb_local/tbb/concurrent_queue.h
diff --git a/inst/include/tbb/concurrent_unordered_map.h b/inst/include/tbb_local/tbb/concurrent_unordered_map.h
similarity index 100%
rename from inst/include/tbb/concurrent_unordered_map.h
rename to inst/include/tbb_local/tbb/concurrent_unordered_map.h
diff --git a/inst/include/tbb/concurrent_unordered_set.h b/inst/include/tbb_local/tbb/concurrent_unordered_set.h
similarity index 100%
rename from inst/include/tbb/concurrent_unordered_set.h
rename to inst/include/tbb_local/tbb/concurrent_unordered_set.h
diff --git a/inst/include/tbb/concurrent_vector.h b/inst/include/tbb_local/tbb/concurrent_vector.h
similarity index 100%
rename from inst/include/tbb/concurrent_vector.h
rename to inst/include/tbb_local/tbb/concurrent_vector.h
diff --git a/inst/include/tbb/critical_section.h b/inst/include/tbb_local/tbb/critical_section.h
similarity index 100%
rename from inst/include/tbb/critical_section.h
rename to inst/include/tbb_local/tbb/critical_section.h
diff --git a/inst/include/tbb/enumerable_thread_specific.h b/inst/include/tbb_local/tbb/enumerable_thread_specific.h
similarity index 100%
rename from inst/include/tbb/enumerable_thread_specific.h
rename to inst/include/tbb_local/tbb/enumerable_thread_specific.h
diff --git a/inst/include/tbb/flow_graph.h b/inst/include/tbb_local/tbb/flow_graph.h
similarity index 100%
rename from inst/include/tbb/flow_graph.h
rename to inst/include/tbb_local/tbb/flow_graph.h
diff --git a/inst/include/tbb/flow_graph_abstractions.h b/inst/include/tbb_local/tbb/flow_graph_abstractions.h
similarity index 100%
rename from inst/include/tbb/flow_graph_abstractions.h
rename to inst/include/tbb_local/tbb/flow_graph_abstractions.h
diff --git a/inst/include/tbb/flow_graph_opencl_node.h b/inst/include/tbb_local/tbb/flow_graph_opencl_node.h
similarity index 100%
rename from inst/include/tbb/flow_graph_opencl_node.h
rename to inst/include/tbb_local/tbb/flow_graph_opencl_node.h
diff --git a/inst/include/tbb/gfx_factory.h b/inst/include/tbb_local/tbb/gfx_factory.h
similarity index 100%
rename from inst/include/tbb/gfx_factory.h
rename to inst/include/tbb_local/tbb/gfx_factory.h
diff --git a/inst/include/tbb/global_control.h b/inst/include/tbb_local/tbb/global_control.h
similarity index 100%
rename from inst/include/tbb/global_control.h
rename to inst/include/tbb_local/tbb/global_control.h
diff --git a/inst/include/tbb/index.html b/inst/include/tbb_local/tbb/index.html
similarity index 100%
rename from inst/include/tbb/index.html
rename to inst/include/tbb_local/tbb/index.html
diff --git a/inst/include/tbb/internal/_aggregator_impl.h b/inst/include/tbb_local/tbb/internal/_aggregator_impl.h
similarity index 100%
rename from inst/include/tbb/internal/_aggregator_impl.h
rename to inst/include/tbb_local/tbb/internal/_aggregator_impl.h
diff --git a/inst/include/tbb/internal/_concurrent_queue_impl.h b/inst/include/tbb_local/tbb/internal/_concurrent_queue_impl.h
similarity index 100%
rename from inst/include/tbb/internal/_concurrent_queue_impl.h
rename to inst/include/tbb_local/tbb/internal/_concurrent_queue_impl.h
diff --git a/inst/include/tbb/internal/_concurrent_unordered_impl.h b/inst/include/tbb_local/tbb/internal/_concurrent_unordered_impl.h
similarity index 100%
rename from inst/include/tbb/internal/_concurrent_unordered_impl.h
rename to inst/include/tbb_local/tbb/internal/_concurrent_unordered_impl.h
diff --git a/inst/include/tbb/internal/_flow_graph_async_msg_impl.h b/inst/include/tbb_local/tbb/internal/_flow_graph_async_msg_impl.h
similarity index 100%
rename from inst/include/tbb/internal/_flow_graph_async_msg_impl.h
rename to inst/include/tbb_local/tbb/internal/_flow_graph_async_msg_impl.h
diff --git a/inst/include/tbb/internal/_flow_graph_body_impl.h b/inst/include/tbb_local/tbb/internal/_flow_graph_body_impl.h
similarity index 100%
rename from inst/include/tbb/internal/_flow_graph_body_impl.h
rename to inst/include/tbb_local/tbb/internal/_flow_graph_body_impl.h
diff --git a/inst/include/tbb/internal/_flow_graph_cache_impl.h b/inst/include/tbb_local/tbb/internal/_flow_graph_cache_impl.h
similarity index 100%
rename from inst/include/tbb/internal/_flow_graph_cache_impl.h
rename to inst/include/tbb_local/tbb/internal/_flow_graph_cache_impl.h
diff --git a/inst/include/tbb/internal/_flow_graph_impl.h b/inst/include/tbb_local/tbb/internal/_flow_graph_impl.h
similarity index 100%
rename from inst/include/tbb/internal/_flow_graph_impl.h
rename to inst/include/tbb_local/tbb/internal/_flow_graph_impl.h
diff --git a/inst/include/tbb/internal/_flow_graph_indexer_impl.h b/inst/include/tbb_local/tbb/internal/_flow_graph_indexer_impl.h
similarity index 100%
rename from inst/include/tbb/internal/_flow_graph_indexer_impl.h
rename to inst/include/tbb_local/tbb/internal/_flow_graph_indexer_impl.h
diff --git a/inst/include/tbb/internal/_flow_graph_item_buffer_impl.h b/inst/include/tbb_local/tbb/internal/_flow_graph_item_buffer_impl.h
similarity index 100%
rename from inst/include/tbb/internal/_flow_graph_item_buffer_impl.h
rename to inst/include/tbb_local/tbb/internal/_flow_graph_item_buffer_impl.h
diff --git a/inst/include/tbb/internal/_flow_graph_join_impl.h b/inst/include/tbb_local/tbb/internal/_flow_graph_join_impl.h
similarity index 100%
rename from inst/include/tbb/internal/_flow_graph_join_impl.h
rename to inst/include/tbb_local/tbb/internal/_flow_graph_join_impl.h
diff --git a/inst/include/tbb/internal/_flow_graph_node_impl.h b/inst/include/tbb_local/tbb/internal/_flow_graph_node_impl.h
similarity index 100%
rename from inst/include/tbb/internal/_flow_graph_node_impl.h
rename to inst/include/tbb_local/tbb/internal/_flow_graph_node_impl.h
diff --git a/inst/include/tbb/internal/_flow_graph_streaming_node.h b/inst/include/tbb_local/tbb/internal/_flow_graph_streaming_node.h
similarity index 100%
rename from inst/include/tbb/internal/_flow_graph_streaming_node.h
rename to inst/include/tbb_local/tbb/internal/_flow_graph_streaming_node.h
diff --git a/inst/include/tbb/internal/_flow_graph_tagged_buffer_impl.h b/inst/include/tbb_local/tbb/internal/_flow_graph_tagged_buffer_impl.h
similarity index 100%
rename from inst/include/tbb/internal/_flow_graph_tagged_buffer_impl.h
rename to inst/include/tbb_local/tbb/internal/_flow_graph_tagged_buffer_impl.h
diff --git a/inst/include/tbb/internal/_flow_graph_trace_impl.h b/inst/include/tbb_local/tbb/internal/_flow_graph_trace_impl.h
similarity index 100%
rename from inst/include/tbb/internal/_flow_graph_trace_impl.h
rename to inst/include/tbb_local/tbb/internal/_flow_graph_trace_impl.h
diff --git a/inst/include/tbb/internal/_flow_graph_types_impl.h b/inst/include/tbb_local/tbb/internal/_flow_graph_types_impl.h
similarity index 100%
rename from inst/include/tbb/internal/_flow_graph_types_impl.h
rename to inst/include/tbb_local/tbb/internal/_flow_graph_types_impl.h
diff --git a/inst/include/tbb/internal/_mutex_padding.h b/inst/include/tbb_local/tbb/internal/_mutex_padding.h
similarity index 100%
rename from inst/include/tbb/internal/_mutex_padding.h
rename to inst/include/tbb_local/tbb/internal/_mutex_padding.h
diff --git a/inst/include/tbb/internal/_range_iterator.h b/inst/include/tbb_local/tbb/internal/_range_iterator.h
similarity index 100%
rename from inst/include/tbb/internal/_range_iterator.h
rename to inst/include/tbb_local/tbb/internal/_range_iterator.h
diff --git a/inst/include/tbb/internal/_tbb_hash_compare_impl.h b/inst/include/tbb_local/tbb/internal/_tbb_hash_compare_impl.h
similarity index 100%
rename from inst/include/tbb/internal/_tbb_hash_compare_impl.h
rename to inst/include/tbb_local/tbb/internal/_tbb_hash_compare_impl.h
diff --git a/inst/include/tbb/internal/_tbb_strings.h b/inst/include/tbb_local/tbb/internal/_tbb_strings.h
similarity index 100%
rename from inst/include/tbb/internal/_tbb_strings.h
rename to inst/include/tbb_local/tbb/internal/_tbb_strings.h
diff --git a/inst/include/tbb/internal/_tbb_trace_impl.h b/inst/include/tbb_local/tbb/internal/_tbb_trace_impl.h
similarity index 100%
rename from inst/include/tbb/internal/_tbb_trace_impl.h
rename to inst/include/tbb_local/tbb/internal/_tbb_trace_impl.h
diff --git a/inst/include/tbb/internal/_tbb_windef.h b/inst/include/tbb_local/tbb/internal/_tbb_windef.h
similarity index 100%
rename from inst/include/tbb/internal/_tbb_windef.h
rename to inst/include/tbb_local/tbb/internal/_tbb_windef.h
diff --git a/inst/include/tbb/internal/_template_helpers.h b/inst/include/tbb_local/tbb/internal/_template_helpers.h
similarity index 100%
rename from inst/include/tbb/internal/_template_helpers.h
rename to inst/include/tbb_local/tbb/internal/_template_helpers.h
diff --git a/inst/include/tbb/internal/_x86_eliding_mutex_impl.h b/inst/include/tbb_local/tbb/internal/_x86_eliding_mutex_impl.h
similarity index 100%
rename from inst/include/tbb/internal/_x86_eliding_mutex_impl.h
rename to inst/include/tbb_local/tbb/internal/_x86_eliding_mutex_impl.h
diff --git a/inst/include/tbb/internal/_x86_rtm_rw_mutex_impl.h b/inst/include/tbb_local/tbb/internal/_x86_rtm_rw_mutex_impl.h
similarity index 100%
rename from inst/include/tbb/internal/_x86_rtm_rw_mutex_impl.h
rename to inst/include/tbb_local/tbb/internal/_x86_rtm_rw_mutex_impl.h
diff --git a/inst/include/tbb/machine/gcc_armv7.h b/inst/include/tbb_local/tbb/machine/gcc_armv7.h
similarity index 100%
rename from inst/include/tbb/machine/gcc_armv7.h
rename to inst/include/tbb_local/tbb/machine/gcc_armv7.h
diff --git a/inst/include/tbb/machine/gcc_generic.h b/inst/include/tbb_local/tbb/machine/gcc_generic.h
similarity index 100%
rename from inst/include/tbb/machine/gcc_generic.h
rename to inst/include/tbb_local/tbb/machine/gcc_generic.h
diff --git a/inst/include/tbb/machine/gcc_ia32_common.h b/inst/include/tbb_local/tbb/machine/gcc_ia32_common.h
similarity index 100%
rename from inst/include/tbb/machine/gcc_ia32_common.h
rename to inst/include/tbb_local/tbb/machine/gcc_ia32_common.h
diff --git a/inst/include/tbb/machine/gcc_itsx.h b/inst/include/tbb_local/tbb/machine/gcc_itsx.h
similarity index 100%
rename from inst/include/tbb/machine/gcc_itsx.h
rename to inst/include/tbb_local/tbb/machine/gcc_itsx.h
diff --git a/inst/include/tbb/machine/ibm_aix51.h b/inst/include/tbb_local/tbb/machine/ibm_aix51.h
similarity index 100%
rename from inst/include/tbb/machine/ibm_aix51.h
rename to inst/include/tbb_local/tbb/machine/ibm_aix51.h
diff --git a/inst/include/tbb/machine/icc_generic.h b/inst/include/tbb_local/tbb/machine/icc_generic.h
similarity index 100%
rename from inst/include/tbb/machine/icc_generic.h
rename to inst/include/tbb_local/tbb/machine/icc_generic.h
diff --git a/inst/include/tbb/machine/linux_common.h b/inst/include/tbb_local/tbb/machine/linux_common.h
similarity index 100%
rename from inst/include/tbb/machine/linux_common.h
rename to inst/include/tbb_local/tbb/machine/linux_common.h
diff --git a/inst/include/tbb/machine/linux_ia32.h b/inst/include/tbb_local/tbb/machine/linux_ia32.h
similarity index 100%
rename from inst/include/tbb/machine/linux_ia32.h
rename to inst/include/tbb_local/tbb/machine/linux_ia32.h
diff --git a/inst/include/tbb/machine/linux_ia64.h b/inst/include/tbb_local/tbb/machine/linux_ia64.h
similarity index 100%
rename from inst/include/tbb/machine/linux_ia64.h
rename to inst/include/tbb_local/tbb/machine/linux_ia64.h
diff --git a/inst/include/tbb/machine/linux_intel64.h b/inst/include/tbb_local/tbb/machine/linux_intel64.h
similarity index 100%
rename from inst/include/tbb/machine/linux_intel64.h
rename to inst/include/tbb_local/tbb/machine/linux_intel64.h
diff --git a/inst/include/tbb/machine/mac_ppc.h b/inst/include/tbb_local/tbb/machine/mac_ppc.h
similarity index 100%
rename from inst/include/tbb/machine/mac_ppc.h
rename to inst/include/tbb_local/tbb/machine/mac_ppc.h
diff --git a/inst/include/tbb/machine/macos_common.h b/inst/include/tbb_local/tbb/machine/macos_common.h
similarity index 100%
rename from inst/include/tbb/machine/macos_common.h
rename to inst/include/tbb_local/tbb/machine/macos_common.h
diff --git a/inst/include/tbb/machine/mic_common.h b/inst/include/tbb_local/tbb/machine/mic_common.h
similarity index 100%
rename from inst/include/tbb/machine/mic_common.h
rename to inst/include/tbb_local/tbb/machine/mic_common.h
diff --git a/inst/include/tbb/machine/msvc_armv7.h b/inst/include/tbb_local/tbb/machine/msvc_armv7.h
similarity index 100%
rename from inst/include/tbb/machine/msvc_armv7.h
rename to inst/include/tbb_local/tbb/machine/msvc_armv7.h
diff --git a/inst/include/tbb/machine/msvc_ia32_common.h b/inst/include/tbb_local/tbb/machine/msvc_ia32_common.h
similarity index 100%
rename from inst/include/tbb/machine/msvc_ia32_common.h
rename to inst/include/tbb_local/tbb/machine/msvc_ia32_common.h
diff --git a/inst/include/tbb/machine/sunos_sparc.h b/inst/include/tbb_local/tbb/machine/sunos_sparc.h
similarity index 100%
rename from inst/include/tbb/machine/sunos_sparc.h
rename to inst/include/tbb_local/tbb/machine/sunos_sparc.h
diff --git a/inst/include/tbb/machine/windows_api.h b/inst/include/tbb_local/tbb/machine/windows_api.h
similarity index 100%
rename from inst/include/tbb/machine/windows_api.h
rename to inst/include/tbb_local/tbb/machine/windows_api.h
diff --git a/inst/include/tbb/machine/windows_ia32.h b/inst/include/tbb_local/tbb/machine/windows_ia32.h
similarity index 100%
rename from inst/include/tbb/machine/windows_ia32.h
rename to inst/include/tbb_local/tbb/machine/windows_ia32.h
diff --git a/inst/include/tbb/machine/windows_intel64.h b/inst/include/tbb_local/tbb/machine/windows_intel64.h
similarity index 100%
rename from inst/include/tbb/machine/windows_intel64.h
rename to inst/include/tbb_local/tbb/machine/windows_intel64.h
diff --git a/inst/include/tbb/machine/xbox360_ppc.h b/inst/include/tbb_local/tbb/machine/xbox360_ppc.h
similarity index 100%
rename from inst/include/tbb/machine/xbox360_ppc.h
rename to inst/include/tbb_local/tbb/machine/xbox360_ppc.h
diff --git a/inst/include/tbb/memory_pool.h b/inst/include/tbb_local/tbb/memory_pool.h
similarity index 100%
rename from inst/include/tbb/memory_pool.h
rename to inst/include/tbb_local/tbb/memory_pool.h
diff --git a/inst/include/tbb/mutex.h b/inst/include/tbb_local/tbb/mutex.h
similarity index 100%
rename from inst/include/tbb/mutex.h
rename to inst/include/tbb_local/tbb/mutex.h
diff --git a/inst/include/tbb/null_mutex.h b/inst/include/tbb_local/tbb/null_mutex.h
similarity index 100%
rename from inst/include/tbb/null_mutex.h
rename to inst/include/tbb_local/tbb/null_mutex.h
diff --git a/inst/include/tbb/null_rw_mutex.h b/inst/include/tbb_local/tbb/null_rw_mutex.h
similarity index 100%
rename from inst/include/tbb/null_rw_mutex.h
rename to inst/include/tbb_local/tbb/null_rw_mutex.h
diff --git a/inst/include/tbb/parallel_do.h b/inst/include/tbb_local/tbb/parallel_do.h
similarity index 100%
rename from inst/include/tbb/parallel_do.h
rename to inst/include/tbb_local/tbb/parallel_do.h
diff --git a/inst/include/tbb/parallel_for.h b/inst/include/tbb_local/tbb/parallel_for.h
similarity index 100%
rename from inst/include/tbb/parallel_for.h
rename to inst/include/tbb_local/tbb/parallel_for.h
diff --git a/inst/include/tbb/parallel_for_each.h b/inst/include/tbb_local/tbb/parallel_for_each.h
similarity index 100%
rename from inst/include/tbb/parallel_for_each.h
rename to inst/include/tbb_local/tbb/parallel_for_each.h
diff --git a/inst/include/tbb/parallel_invoke.h b/inst/include/tbb_local/tbb/parallel_invoke.h
similarity index 100%
rename from inst/include/tbb/parallel_invoke.h
rename to inst/include/tbb_local/tbb/parallel_invoke.h
diff --git a/inst/include/tbb/parallel_reduce.h b/inst/include/tbb_local/tbb/parallel_reduce.h
similarity index 100%
rename from inst/include/tbb/parallel_reduce.h
rename to inst/include/tbb_local/tbb/parallel_reduce.h
diff --git a/inst/include/tbb/parallel_scan.h b/inst/include/tbb_local/tbb/parallel_scan.h
similarity index 100%
rename from inst/include/tbb/parallel_scan.h
rename to inst/include/tbb_local/tbb/parallel_scan.h
diff --git a/inst/include/tbb/parallel_sort.h b/inst/include/tbb_local/tbb/parallel_sort.h
similarity index 100%
rename from inst/include/tbb/parallel_sort.h
rename to inst/include/tbb_local/tbb/parallel_sort.h
diff --git a/inst/include/tbb/parallel_while.h b/inst/include/tbb_local/tbb/parallel_while.h
similarity index 100%
rename from inst/include/tbb/parallel_while.h
rename to inst/include/tbb_local/tbb/parallel_while.h
diff --git a/inst/include/tbb/partitioner.h b/inst/include/tbb_local/tbb/partitioner.h
similarity index 100%
rename from inst/include/tbb/partitioner.h
rename to inst/include/tbb_local/tbb/partitioner.h
diff --git a/inst/include/tbb/pipeline.h b/inst/include/tbb_local/tbb/pipeline.h
similarity index 100%
rename from inst/include/tbb/pipeline.h
rename to inst/include/tbb_local/tbb/pipeline.h
diff --git a/inst/include/tbb/queuing_mutex.h b/inst/include/tbb_local/tbb/queuing_mutex.h
similarity index 100%
rename from inst/include/tbb/queuing_mutex.h
rename to inst/include/tbb_local/tbb/queuing_mutex.h
diff --git a/inst/include/tbb/queuing_rw_mutex.h b/inst/include/tbb_local/tbb/queuing_rw_mutex.h
similarity index 100%
rename from inst/include/tbb/queuing_rw_mutex.h
rename to inst/include/tbb_local/tbb/queuing_rw_mutex.h
diff --git a/inst/include/tbb/reader_writer_lock.h b/inst/include/tbb_local/tbb/reader_writer_lock.h
similarity index 100%
rename from inst/include/tbb/reader_writer_lock.h
rename to inst/include/tbb_local/tbb/reader_writer_lock.h
diff --git a/inst/include/tbb/recursive_mutex.h b/inst/include/tbb_local/tbb/recursive_mutex.h
similarity index 100%
rename from inst/include/tbb/recursive_mutex.h
rename to inst/include/tbb_local/tbb/recursive_mutex.h
diff --git a/inst/include/tbb/runtime_loader.h b/inst/include/tbb_local/tbb/runtime_loader.h
similarity index 100%
rename from inst/include/tbb/runtime_loader.h
rename to inst/include/tbb_local/tbb/runtime_loader.h
diff --git a/inst/include/tbb/scalable_allocator.h b/inst/include/tbb_local/tbb/scalable_allocator.h
similarity index 100%
rename from inst/include/tbb/scalable_allocator.h
rename to inst/include/tbb_local/tbb/scalable_allocator.h
diff --git a/inst/include/tbb/spin_mutex.h b/inst/include/tbb_local/tbb/spin_mutex.h
similarity index 100%
rename from inst/include/tbb/spin_mutex.h
rename to inst/include/tbb_local/tbb/spin_mutex.h
diff --git a/inst/include/tbb/spin_rw_mutex.h b/inst/include/tbb_local/tbb/spin_rw_mutex.h
similarity index 100%
rename from inst/include/tbb/spin_rw_mutex.h
rename to inst/include/tbb_local/tbb/spin_rw_mutex.h
diff --git a/inst/include/tbb/task.h b/inst/include/tbb_local/tbb/task.h
similarity index 100%
rename from inst/include/tbb/task.h
rename to inst/include/tbb_local/tbb/task.h
diff --git a/inst/include/tbb/task_arena.h b/inst/include/tbb_local/tbb/task_arena.h
similarity index 100%
rename from inst/include/tbb/task_arena.h
rename to inst/include/tbb_local/tbb/task_arena.h
diff --git a/inst/include/tbb/task_group.h b/inst/include/tbb_local/tbb/task_group.h
similarity index 100%
rename from inst/include/tbb/task_group.h
rename to inst/include/tbb_local/tbb/task_group.h
diff --git a/inst/include/tbb/task_scheduler_init.h b/inst/include/tbb_local/tbb/task_scheduler_init.h
similarity index 100%
rename from inst/include/tbb/task_scheduler_init.h
rename to inst/include/tbb_local/tbb/task_scheduler_init.h
diff --git a/inst/include/tbb/task_scheduler_observer.h b/inst/include/tbb_local/tbb/task_scheduler_observer.h
similarity index 100%
rename from inst/include/tbb/task_scheduler_observer.h
rename to inst/include/tbb_local/tbb/task_scheduler_observer.h
diff --git a/inst/include/tbb/tbb.h b/inst/include/tbb_local/tbb/tbb.h
similarity index 100%
rename from inst/include/tbb/tbb.h
rename to inst/include/tbb_local/tbb/tbb.h
diff --git a/inst/include/tbb/tbb_allocator.h b/inst/include/tbb_local/tbb/tbb_allocator.h
similarity index 100%
rename from inst/include/tbb/tbb_allocator.h
rename to inst/include/tbb_local/tbb/tbb_allocator.h
diff --git a/inst/include/tbb/tbb_config.h b/inst/include/tbb_local/tbb/tbb_config.h
similarity index 100%
rename from inst/include/tbb/tbb_config.h
rename to inst/include/tbb_local/tbb/tbb_config.h
diff --git a/inst/include/tbb/tbb_disable_exceptions.h b/inst/include/tbb_local/tbb/tbb_disable_exceptions.h
similarity index 100%
rename from inst/include/tbb/tbb_disable_exceptions.h
rename to inst/include/tbb_local/tbb/tbb_disable_exceptions.h
diff --git a/inst/include/tbb/tbb_exception.h b/inst/include/tbb_local/tbb/tbb_exception.h
similarity index 100%
rename from inst/include/tbb/tbb_exception.h
rename to inst/include/tbb_local/tbb/tbb_exception.h
diff --git a/inst/include/tbb/tbb_machine.h b/inst/include/tbb_local/tbb/tbb_machine.h
similarity index 100%
rename from inst/include/tbb/tbb_machine.h
rename to inst/include/tbb_local/tbb/tbb_machine.h
diff --git a/inst/include/tbb/tbb_profiling.h b/inst/include/tbb_local/tbb/tbb_profiling.h
similarity index 100%
rename from inst/include/tbb/tbb_profiling.h
rename to inst/include/tbb_local/tbb/tbb_profiling.h
diff --git a/inst/include/tbb/tbb_stddef.h b/inst/include/tbb_local/tbb/tbb_stddef.h
similarity index 100%
rename from inst/include/tbb/tbb_stddef.h
rename to inst/include/tbb_local/tbb/tbb_stddef.h
diff --git a/inst/include/tbb/tbb_thread.h b/inst/include/tbb_local/tbb/tbb_thread.h
similarity index 100%
rename from inst/include/tbb/tbb_thread.h
rename to inst/include/tbb_local/tbb/tbb_thread.h
diff --git a/inst/include/tbb/tbbmalloc_proxy.h b/inst/include/tbb_local/tbb/tbbmalloc_proxy.h
similarity index 100%
rename from inst/include/tbb/tbbmalloc_proxy.h
rename to inst/include/tbb_local/tbb/tbbmalloc_proxy.h
diff --git a/inst/include/tbb/tick_count.h b/inst/include/tbb_local/tbb/tick_count.h
similarity index 100%
rename from inst/include/tbb/tick_count.h
rename to inst/include/tbb_local/tbb/tick_count.h
diff --git a/man/RcppParallel-package.Rd b/man/RcppParallel-package.Rd
index 7ebea999..ddb46d34 100644
--- a/man/RcppParallel-package.Rd
+++ b/man/RcppParallel-package.Rd
@@ -15,7 +15,7 @@
   Blocks). On other platforms a less-performant fallback implementation based on the
   TinyThread library is used.
   
-  For additional documentation see the package website at: \href{http://rcppcore.github.io/RcppParallel}{http://rcppcore.github.io/RcppParallel}.
+  For additional documentation see the package website at: \href{https://rcppcore.github.io/RcppParallel/}{https://rcppcore.github.io/RcppParallel/}.
 }
 
 \author{
diff --git a/src/Makevars.in b/src/Makevars.in
index 56c601ee..e7f0ad73 100644
--- a/src/Makevars.in
+++ b/src/Makevars.in
@@ -1,7 +1,16 @@
 
-PKG_CPPFLAGS = -I../inst/include
 PKG_CXXFLAGS = @CXX11STD@
 
+ifdef TBB_INC
+PKG_CPPFLAGS = -I../inst/include -I$(TBB_INC)
+else
+PKG_CPPFLAGS = -I../inst/include
+endif
+
+ifdef TBB_LIB
+PKG_LIBS = -Wl,-L,"$(TBB_LIB)" -Wl,-rpath,"$(TBB_LIB)" -ltbb -ltbbmalloc
+endif
+
 ifeq ($(OS), Windows_NT)
 
   USE_TBB=Windows
@@ -86,7 +95,21 @@ endif
 all: tbb $(SHLIB)
 
 tbb:
+ifdef TBB_LIB
+	echo "Using system (Intel/OneAPI) TBB library..."; \
 	mkdir -p ../inst/lib/$(ARCH_DIR); \
+	cp $(TBB_LIB)/libtbb.so ../inst/lib/$(ARCH_DIR)/libtbb.so 2>/dev/null || :; \
+	cp $(TBB_LIB)/libtbbmalloc.so ../inst/lib/$(ARCH_DIR)/libtbbmalloc.so 2>/dev/null || :; \
+	rm -Rf ../inst/include/serial/ ../inst/include/tbb/; \
+	rm -Rf ../inst/include/tbb_local/; \
+	mkdir -p ../inst/include; \
+	cp -R $(TBB_INC)/serial ../inst/include/ 2>/dev/null || :; \
+	cp -R $(TBB_INC)/tbb ../inst/include/ 2>/dev/null || :
+else
+	echo "Building TBB library from source code..."; \
+	mkdir -p ../inst/lib/$(ARCH_DIR); \
+	cp -R ../inst/include/tbb_local/* ../inst/include/; \
+	rm -Rf ../inst/include/tbb_local/; \
 	cd tbb/src; \
 	if [ -n "$(shell echo $(CC) | grep clang)" ]; then \
 	   $(MAKE_CMD) stdver=@STDVER@ compiler=clang $(MAKE_ARGS); \
@@ -97,9 +120,14 @@ tbb:
 	fi; \
 	cd ../..; \
 	cp tbb/build/lib_release/$(TBB_COPY_PATTERN) ../inst/lib/$(ARCH_DIR)
+endif
 
 clean:
+ifdef TBB_LIB
+	echo "Nothing to clean for TBB."
+else
 	(cd tbb/src; make clean)
-
 endif
 
+
+endif
diff --git a/src/options.cpp b/src/options.cpp
index 8a4168dd..56b9636b 100644
--- a/src/options.cpp
+++ b/src/options.cpp
@@ -10,7 +10,11 @@
 
 extern "C" SEXP defaultNumThreads() {
    SEXP threadsSEXP = Rf_allocVector(INTSXP, 1);
+#ifndef __TBB_tbb_stddef_H
+   INTEGER(threadsSEXP)[0] = tbb::this_task_arena::max_concurrency();
+#else
    INTEGER(threadsSEXP)[0] = tbb::task_scheduler_init::default_num_threads();
+#endif
    return threadsSEXP;
 }