diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs
index fe75ee8b37b8d..4c54d13dbce8c 100644
--- a/compiler/rustc_interface/src/tests.rs
+++ b/compiler/rustc_interface/src/tests.rs
@@ -66,6 +66,7 @@ where
         location: ExternLocation::ExactPaths(locations),
         is_private_dep: false,
         add_prelude: true,
+        sysroot_dep: false,
     }
 }
 
diff --git a/compiler/rustc_metadata/src/creader.rs b/compiler/rustc_metadata/src/creader.rs
index a9e3b55aeeedf..1e039b40b8762 100644
--- a/compiler/rustc_metadata/src/creader.rs
+++ b/compiler/rustc_metadata/src/creader.rs
@@ -908,6 +908,10 @@ impl<'a> CrateLoader<'a> {
                 // Don't worry about pathless `--extern foo` sysroot references
                 continue;
             }
+            if entry.sysroot_dep {
+                // If it's an explicit sysroot dependency, let it slide
+                continue;
+            }
             let name_interned = Symbol::intern(name);
             if self.used_extern_options.contains(&name_interned) {
                 continue;
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index 5a447aa623734..2b0a6bc10d791 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -477,6 +477,14 @@ pub struct ExternEntry {
     /// This can be disabled with the `noprelude` option like
     /// `--extern noprelude:name`.
     pub add_prelude: bool,
+    /// The extern entry is an explicitly listed sysroot crate.
+    ///
+    /// `--extern sysroot:std=/path/to/lib/libstd.rlib`
+    /// This is useful for when the build system is using explicit sysroot
+    /// dependencies rather than allowing rustc to find them implicitly. This is
+    /// primarily used to suppress `unused-crate-dependencies` warnings, since
+    /// these dependencies are added unconditionally.
+    pub sysroot_dep: bool,
 }
 
 #[derive(Clone, Debug)]
@@ -536,7 +544,7 @@ impl Externs {
 
 impl ExternEntry {
     fn new(location: ExternLocation) -> ExternEntry {
-        ExternEntry { location, is_private_dep: false, add_prelude: false }
+        ExternEntry { location, is_private_dep: false, add_prelude: false, sysroot_dep: false }
     }
 
     pub fn files(&self) -> Option<impl Iterator<Item = &CanonicalizedPath>> {
@@ -2186,6 +2194,7 @@ pub fn parse_externs(
 
         let mut is_private_dep = false;
         let mut add_prelude = true;
+        let mut sysroot_dep = false;
         if let Some(opts) = options {
             if !is_unstable_enabled {
                 early_error(
@@ -2207,6 +2216,7 @@ pub fn parse_externs(
                             );
                         }
                     }
+                    "sysroot" => sysroot_dep = true,
                     _ => early_error(error_format, &format!("unknown --extern option `{opt}`")),
                 }
             }
@@ -2215,6 +2225,8 @@ pub fn parse_externs(
         // Crates start out being not private, and go to being private `priv`
         // is specified.
         entry.is_private_dep |= is_private_dep;
+        // likewise `sysroot`
+        entry.sysroot_dep |= sysroot_dep;
         // If any flag is missing `noprelude`, then add to the prelude.
         entry.add_prelude |= add_prelude;
     }
diff --git a/src/test/ui/extern-flag/no-sysroot.rs b/src/test/ui/extern-flag/no-sysroot.rs
new file mode 100644
index 0000000000000..871599bdf4832
--- /dev/null
+++ b/src/test/ui/extern-flag/no-sysroot.rs
@@ -0,0 +1,6 @@
+// aux-crate:somedep=somedep.rs
+// compile-flags: -Zunstable-options -Dunused-crate-dependencies
+// edition:2018
+
+fn main() { //~ ERROR external crate `somedep` unused in `no_sysroot`
+}
diff --git a/src/test/ui/extern-flag/no-sysroot.stderr b/src/test/ui/extern-flag/no-sysroot.stderr
new file mode 100644
index 0000000000000..f0ac451a4dd2c
--- /dev/null
+++ b/src/test/ui/extern-flag/no-sysroot.stderr
@@ -0,0 +1,11 @@
+error: external crate `somedep` unused in `no_sysroot`: remove the dependency or add `use somedep as _;`
+  --> $DIR/no-sysroot.rs:5:1
+   |
+LL | fn main() {
+   | ^
+   |
+   = note: requested on the command line with `-D unused-crate-dependencies`
+   = help: remove unnecessary dependency `somedep`
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/extern-flag/sysroot.rs b/src/test/ui/extern-flag/sysroot.rs
new file mode 100644
index 0000000000000..a068700b483dc
--- /dev/null
+++ b/src/test/ui/extern-flag/sysroot.rs
@@ -0,0 +1,7 @@
+// check-pass
+// aux-crate:sysroot:somedep=somedep.rs
+// compile-flags: -Zunstable-options -Dunused-crate-dependencies
+// edition:2018
+
+fn main() {
+}