diff --git a/numpy/core/setup.py b/numpy/core/setup.py
index 1042a1c4520d..c973e96c6d62 100644
--- a/numpy/core/setup.py
+++ b/numpy/core/setup.py
@@ -944,7 +944,7 @@ def generate_umath_c(ext, build_dir):
             join(codegen_dir, 'generate_ufunc_api.py'),
             ]
 
-    config.add_extension('_multiarray_umath',
+    config.add_hpy_extension('_multiarray_umath',
                          sources=multiarray_src + umath_src +
                                  common_src +
                                  [generate_config_h,
diff --git a/numpy/core/src/multiarray/arrayobject.c b/numpy/core/src/multiarray/arrayobject.c
index 199626144b28..2052d252d373 100644
--- a/numpy/core/src/multiarray/arrayobject.c
+++ b/numpy/core/src/multiarray/arrayobject.c
@@ -23,6 +23,7 @@ maintainer email:  oliphant.travis@ieee.org
 #define PY_SSIZE_T_CLEAN
 #include <Python.h>
 #include "structmember.h"
+#include "hpy.h"
 
 /*#include <stdio.h>*/
 #define NPY_NO_DEPRECATED_API NPY_API_VERSION
@@ -1821,9 +1822,9 @@ static PyType_Slot PyArray_Type_slots[] = {
     {0, NULL},
 };
 
-NPY_NO_EXPORT PyType_Spec PyArray_Type_spec = {
+NPY_NO_EXPORT HPyType_Spec PyArray_Type_spec = {
     .name = "numpy.ndarray",
     .basicsize = sizeof(PyArrayObject_fields),
-    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE),
-    .slots = PyArray_Type_slots,
+    .flags = (HPy_TPFLAGS_DEFAULT | HPy_TPFLAGS_BASETYPE),
+    .legacy_slots = PyArray_Type_slots,
 };
diff --git a/numpy/core/src/multiarray/arrayobject.h b/numpy/core/src/multiarray/arrayobject.h
index afd5e8e87f1f..d559978dd8e5 100644
--- a/numpy/core/src/multiarray/arrayobject.h
+++ b/numpy/core/src/multiarray/arrayobject.h
@@ -5,6 +5,8 @@
 #error You should not include this
 #endif
 
+#include "hpy.h"
+
 NPY_NO_EXPORT PyObject *
 _strings_richcompare(PyArrayObject *self, PyArrayObject *other, int cmp_op,
                      int rstrip);
@@ -26,6 +28,6 @@ array_might_be_written(PyArrayObject *obj);
  */
 static const int NPY_ARRAY_WARN_ON_WRITE = (1 << 31);
 
-extern NPY_NO_EXPORT PyType_Spec PyArray_Type_spec;
+extern NPY_NO_EXPORT HPyType_Spec PyArray_Type_spec;
 
 #endif
diff --git a/numpy/core/src/multiarray/multiarraymodule.c b/numpy/core/src/multiarray/multiarraymodule.c
index cb1de8bc2b0d..a95dc9e4a66a 100644
--- a/numpy/core/src/multiarray/multiarraymodule.c
+++ b/numpy/core/src/multiarray/multiarraymodule.c
@@ -17,6 +17,7 @@
 #define PY_SSIZE_T_CLEAN
 #include "Python.h"
 #include "structmember.h"
+#include "hpy.h"
 
 #define NPY_NO_DEPRECATED_API NPY_API_VERSION
 #define _UMATHMODULE
@@ -4510,7 +4511,10 @@ intern_strings(void)
 
 static struct PyModuleDef moduledef = {
         PyModuleDef_HEAD_INIT,
-        "_multiarray_umath",
+        /* XXX: Unclear if a dotted name is legit in .m_name, but universal
+         * mode requires it.
+         */
+        "numpy.core._multiarray_umath",
         NULL,
         -1,
         array_module_methods,
@@ -4521,7 +4525,8 @@ static struct PyModuleDef moduledef = {
 };
 
 /* Initialization function for the module */
-PyMODINIT_FUNC PyInit__multiarray_umath(void) {
+HPy_MODINIT(_multiarray_umath)
+static HPy init__multiarray_umath_impl(HPyContext ctx) {
     PyObject *m, *d, *s;
     PyObject *c_api;
 
@@ -4588,13 +4593,14 @@ PyMODINIT_FUNC PyInit__multiarray_umath(void) {
         goto err;
     }
 
-    PyObject *array_type = PyType_FromSpec(&PyArray_Type_spec);
-    if (array_type == NULL) {
+    HPy h_array_type = HPyType_FromSpec(ctx, &PyArray_Type_spec, NULL);
+    if (HPy_IsNull(h_array_type)) {
         goto err;
     }
-    _PyArray_Type_p = (PyTypeObject*)array_type;
+    _PyArray_Type_p = (PyTypeObject*)HPy_AsPyObject(ctx, h_array_type);
     PyArray_Type.tp_as_buffer = &array_as_buffer;
     PyArray_Type.tp_weaklistoffset = offsetof(PyArrayObject_fields, weakreflist);
+    HPy_Close(ctx, h_array_type);
 
     if (setup_scalartypes(d) < 0) {
         goto err;
@@ -4725,7 +4731,7 @@ PyMODINIT_FUNC PyInit__multiarray_umath(void) {
     ADDCONST(MAY_SHARE_EXACT);
 #undef ADDCONST
 
-    PyDict_SetItemString(d, "ndarray", array_type);
+    PyDict_SetItemString(d, "ndarray", (PyObject*)&PyArray_Type);
     PyDict_SetItemString(d, "flatiter", (PyObject *)&PyArrayIter_Type);
     PyDict_SetItemString(d, "nditer", (PyObject *)&NpyIter_Type);
     PyDict_SetItemString(d, "broadcast",
@@ -4767,12 +4773,12 @@ PyMODINIT_FUNC PyInit__multiarray_umath(void) {
     if (initumath(m) != 0) {
         goto err;
     }
-    return m;
+    return HPy_FromPyObject(ctx, m);
 
  err:
     if (!PyErr_Occurred()) {
         PyErr_SetString(PyExc_RuntimeError,
                         "cannot load multiarray module.");
     }
-    return NULL;
+    return HPy_NULL;
 }
diff --git a/numpy/ctypeslib.py b/numpy/ctypeslib.py
index e8f7750fe5ff..712eb6c7c6f9 100644
--- a/numpy/ctypeslib.py
+++ b/numpy/ctypeslib.py
@@ -132,6 +132,7 @@ def load_library(libname, loader_path):
             so_ext2 = get_shared_lib_extension(is_python_ext=True)
             if not so_ext2 == so_ext:
                 libname_ext.insert(0, libname + so_ext2)
+            libname_ext.insert(0, libname + '.hpy.so')
         else:
             libname_ext = [libname]
 
diff --git a/numpy/distutils/command/build_ext.py b/numpy/distutils/command/build_ext.py
index ca6f8bcd24d6..906db0eb1fed 100644
--- a/numpy/distutils/command/build_ext.py
+++ b/numpy/distutils/command/build_ext.py
@@ -6,7 +6,7 @@
 from glob import glob
 
 from distutils.dep_util import newer_group
-from distutils.command.build_ext import build_ext as old_build_ext
+from setuptools.command.build_ext import build_ext as old_build_ext
 from distutils.errors import DistutilsFileError, DistutilsSetupError,\
     DistutilsError
 from distutils.file_util import copy_file
@@ -543,6 +543,10 @@ def build_extension(self, ext):
                build_temp=self.build_temp,
                target_lang=ext.language)
 
+        if ext._needs_stub:
+            cmd = self.get_finalized_command('build_py').build_lib
+            self.write_stub(cmd, ext)
+
     def _add_dummy_mingwex_sym(self, c_sources):
         build_src = self.get_finalized_command("build_src").build_src
         build_clib = self.get_finalized_command("build_clib").build_clib
diff --git a/numpy/distutils/misc_util.py b/numpy/distutils/misc_util.py
index 5392663d65ae..44f7571adb43 100644
--- a/numpy/distutils/misc_util.py
+++ b/numpy/distutils/misc_util.py
@@ -726,7 +726,8 @@ def get_frame(level=0):
 
 class Configuration:
 
-    _list_keys = ['packages', 'ext_modules', 'data_files', 'include_dirs',
+    _list_keys = ['packages', 'ext_modules', 'hpy_ext_modules', 'data_files',
+                  'include_dirs',
                   'libraries', 'headers', 'scripts', 'py_modules',
                   'installed_libraries', 'define_macros']
     _dict_keys = ['package_dir', 'installed_pkg_config']
@@ -1456,6 +1457,31 @@ def add_extension(self,name,sources,**kw):
         The self.paths(...) method is applied to all lists that may contain
         paths.
         """
+        from numpy.distutils.core import Extension
+        ext_args = self._process_extension_args(name, sources, **kw)
+        ext = Extension(**ext_args)
+        self.ext_modules.append(ext)
+
+        dist = self.get_distribution()
+        if dist is not None:
+            self.warn('distutils distribution has been initialized,'\
+                      ' it may be too late to add an extension '+name)
+        return ext
+
+    def add_hpy_extension(self, name, sources, **kw):
+        from numpy.distutils.core import Extension
+        ext_args = self._process_extension_args(name, sources, **kw)
+        ext = Extension(**ext_args)
+        self.hpy_ext_modules.append(ext)
+
+        dist = self.get_distribution()
+        if dist is not None:
+            self.warn('distutils distribution has been initialized,'\
+                      ' it may be too late to add an extension '+name)
+        return ext
+
+
+    def _process_extension_args(self, name, sources, **kw):
         ext_args = copy.copy(kw)
         ext_args['name'] = dot_join(self.name, name)
         ext_args['sources'] = sources
@@ -1500,16 +1526,7 @@ def add_extension(self,name,sources,**kw):
         ext_args['libraries'] = libnames + ext_args['libraries']
         ext_args['define_macros'] = \
             self.define_macros + ext_args.get('define_macros', [])
-
-        from numpy.distutils.core import Extension
-        ext = Extension(**ext_args)
-        self.ext_modules.append(ext)
-
-        dist = self.get_distribution()
-        if dist is not None:
-            self.warn('distutils distribution has been initialized,'\
-                      ' it may be too late to add an extension '+name)
-        return ext
+        return ext_args
 
     def add_library(self,name,sources,**build_info):
         """
diff --git a/pyproject.toml b/pyproject.toml
index 2526842fa24b..bb2de0018e42 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,6 +4,7 @@ requires = [
     "setuptools<49.2.0",
     "wheel<=0.35.1",
     "Cython>=0.29.21,<3.0",  # Note: keep in sync with tools/cythonize.py
+    "hpy.devel @ git+https://github.com/hpyproject/hpy.git@8e20b89116c2993188157c09a6070a64f8efbd82#egg=hpy.devel"
 ]
 
 
diff --git a/setup.py b/setup.py
index 6033916c2595..6b42dd551b6a 100755
--- a/setup.py
+++ b/setup.py
@@ -363,6 +363,7 @@ def get_docs_url():
         # to the associated docs easily.
         return "https://numpy.org/doc/{}.{}".format(MAJOR, MINOR)
 
+HPY_ABI = 'cpython' if sys.implementation.name == 'cpython' else 'universal'
 
 def setup_package():
     src_path = os.path.dirname(os.path.abspath(__file__))
@@ -405,6 +406,11 @@ def setup_package():
         cmdclass=cmdclass,
         python_requires='>=3.7',
         zip_safe=False,
+        setup_requires=['hpy.devel'],
+        # distuils doesn't load hpy.devel unless hpy_ext_modules is present
+        # as a keyword
+        hpy_ext_modules=[],
+        hpy_abi=HPY_ABI,
         entry_points={
             'console_scripts': f2py_cmds
         },
diff --git a/test_requirements.txt b/test_requirements.txt
index 496cb3a09e5c..9ba1465b7d21 100644
--- a/test_requirements.txt
+++ b/test_requirements.txt
@@ -13,3 +13,5 @@ cffi
 # - Mypy doesn't currently work on Python 3.9
 mypy==0.790; platform_python_implementation != "PyPy"
 typing_extensions
+# HPy
+git+https://github.com/hpyproject/hpy.git@8e20b89116c2993188157c09a6070a64f8efbd82#egg=hpy.devel
diff --git a/tools/travis-before-install.sh b/tools/travis-before-install.sh
index 81737af89e64..d4b36e91bfcd 100755
--- a/tools/travis-before-install.sh
+++ b/tools/travis-before-install.sh
@@ -49,6 +49,7 @@ pip install --upgrade pip 'setuptools<49.2.0' wheel
 # requirement using `grep cython test_requirements.txt` instead of simply
 # writing 'pip install setuptools wheel cython'.
 pip install `grep cython test_requirements.txt`
+pip install `grep hpy.devel test_requirements.txt`
 
 if [ -n "$DOWNLOAD_OPENBLAS" ]; then
   pwd
diff --git a/tools/travis-test.sh b/tools/travis-test.sh
index 6d8d147572f0..9c68e7bfd184 100755
--- a/tools/travis-test.sh
+++ b/tools/travis-test.sh
@@ -25,7 +25,8 @@ if [ -n "$PYTHON_OPTS" ]; then
 fi
 
 # make some warnings fatal, mostly to match windows compilers
-werrors="-Werror=vla -Werror=nonnull -Werror=pointer-arith"
+# werrors="-Werror=vla -Werror=nonnull -Werror=pointer-arith"
+werrors="-Werror=nonnull -Werror=pointer-arith"
 werrors="$werrors -Werror=implicit-function-declaration"
 
 # build with c99 by default