diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 42e6a9d..a01a78a 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -6,9 +6,10 @@ permissions:
   contents: read
 
 env:
-  CIBW_BEFORE_BUILD: pip install setuptools oldest-supported-numpy
+  CIBW_BEFORE_BUILD: pip install setuptools oldest-supported-numpy pytest
+  CIBW_BEFORE_TEST: pip install pytest
   CIBW_BUILD_VERBOSITY: 1
-  CIBW_TEST_COMMAND: python -c "import sys, numexpr; sys.exit(0 if numexpr.test().wasSuccessful() else 1)"
+  CIBW_TEST_COMMAND: pytest --pyargs numexpr
   CIBW_TEST_SKIP: "*macosx*arm64*"
   # Building for musllinux and aarch64 takes way too much time.
   # Moreover, NumPy is not providing musllinux for x86_64 either, so it's not worth it.
@@ -16,7 +17,7 @@ env:
 
 jobs:
   build_wheels:
-    name: Build wheels on ${{ matrix.os }} for ${{ matrix.arch }} - ${{ matrix.p_ver }}
+    name: Build wheels on ${{ matrix.os }} for ${{ matrix.arch }} - ${{ matrix.cibw_build }}
     runs-on: ${{ matrix.os }}
     permissions:
       contents: write
@@ -24,12 +25,14 @@ jobs:
       CIBW_BUILD: ${{ matrix.cibw_build }}
       CIBW_ARCHS_LINUX: ${{ matrix.arch }}
       CIBW_ARCHS_MACOS: "x86_64 arm64"
+      CIBW_ENABLE: cpython-freethreading
     strategy:
+      fail-fast: false
       matrix:
         os: [ubuntu-latest, windows-latest, macos-latest]
         arch: [x86_64, aarch64]
-        cibw_build: ["cp3{10,11,12,13}-*"]
-        p_ver: ["3.10-3.13"]
+        cibw_build: ["cp3{10,11,12,13}-*", "cp313t-*"]
+        p_ver: ["3.10-3.13+3.13t"]
         exclude:
           - os: windows-latest
             arch: aarch64
@@ -53,6 +56,15 @@ jobs:
         if: ${{ matrix.arch == 'aarch64' }}
         name: Set up QEMU
 
+      - name: Setup free-threading variables
+        if: ${{ endsWith(matrix.cibw_build, 't-*') }}
+        shell: bash -l {0}
+        run: |
+          echo "CIBW_BEFORE_BUILD=pip install setuptools numpy" >> "$GITHUB_ENV"
+          echo "CIBW_BEFORE_TEST=pip install pytest pytest-run-parallel" >> "$GITHUB_ENV"
+          echo "CIBW_TEST_COMMAND=pytest --parallel-threads=4 --pyargs numexpr" >> "$GITHUB_ENV"
+          echo "ARTIFACT_LABEL=freethreaded" >> "$GITHUB_ENV"
+
       - name: Build wheels
         run: |
           python -m cibuildwheel --output-dir wheelhouse
@@ -66,6 +78,7 @@ jobs:
       - uses: actions/upload-artifact@v4
         with:
           path: ./wheelhouse/*
+          name: numexpr-${{ matrix.os }}-${{ matrix.arch }}-${{ env.ARTIFACT_LABEL || 'standard' }}
 
       - name: Upload to GitHub Release
         uses: softprops/action-gh-release@v1
diff --git a/.gitignore b/.gitignore
index 928bf15..7bf6f98 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,6 +7,7 @@ artifact/
 numexpr.egg-info/
 *.pyc
 *.swp
+*.so
 *~
 doc/_build
 site.cfg
diff --git a/README.rst b/README.rst
index 9033d51..264fd2b 100644
--- a/README.rst
+++ b/README.rst
@@ -159,6 +159,24 @@ Usage
   array([ True, False, False], dtype=bool)
 
 
+Free-threading support
+----------------------
+Starting on CPython 3.13 onwards there is a new distribution that disables the
+Global Interpreter Lock (GIL) altogether, thus increasing the performance yields
+under multi-threaded conditions on a single interpreter, as opposed to having to use
+multiprocessing.
+
+Whilst numexpr has been demonstrated to work under free-threaded
+CPython, considerations need to be taken when using numexpr native parallel
+implementation vs using Python threads directly in order to prevent oversubscription,
+we recommend either using the main CPython interpreter thread to spawn multiple C threads
+using the parallel numexpr API, or spawning multiple CPython threads that do not use
+the parallel API.
+
+For more information about free-threaded CPython, we recommend visiting the following
+`community Wiki <https://py-free-threading.github.io/>`
+
+
 Documentation
 -------------
 
diff --git a/numexpr/interpreter.cpp b/numexpr/interpreter.cpp
index edebd71..32f6c37 100644
--- a/numexpr/interpreter.cpp
+++ b/numexpr/interpreter.cpp
@@ -556,7 +556,7 @@ stringcontains(const char *haystack_start, const char *needle_start, npy_intp ma
 
     size_t si = 0;
     size_t min_len = min(needle_len, haystack_len);
-    while (*haystack && *needle && si < min_len)
+    while (si < min_len && *haystack && *needle)
     {
       ok &= *haystack++ == *needle++;
       si++;
@@ -573,7 +573,7 @@ stringcontains(const char *haystack_start, const char *needle_start, npy_intp ma
     }
 
     /* calc haystack length */
-    while (*haystack && si < haystack_len) {
+    while (si < haystack_len && *haystack) {
         haystack++;
         si++;
     }
@@ -652,6 +652,7 @@ int vm_engine_iter_task(NpyIter *iter, npy_intp *memsteps,
 
     /* Then finish off the rest */
     if (block_size > 0) do {
+        block_size = *size_ptr;
 #define REDUCTION_INNER_LOOP
 #define BLOCK_SIZE block_size
 #include "interp_body.cpp"
@@ -698,6 +699,7 @@ vm_engine_iter_outer_reduce_task(NpyIter *iter, npy_intp *memsteps,
 
     /* Then finish off the rest */
     if (block_size > 0) do {
+        block_size = *size_ptr;
 #define BLOCK_SIZE block_size
 #define NO_OUTPUT_BUFFERING // Because it's a reduction
 #include "interp_body.cpp"
diff --git a/numexpr/module.cpp b/numexpr/module.cpp
index 66b5b77..a42042b 100644
--- a/numexpr/module.cpp
+++ b/numexpr/module.cpp
@@ -47,11 +47,14 @@ void *th_worker(void *tidptr)
     char **errmsg;
     // For output buffering if needed
     vector<char> out_buffer;
+    int init_sentinels_done = 0;
 
     while (1) {
 
         /* Sentinels have to be initialised yet */
-        gs.init_sentinels_done = 0;
+        if (tid == 0) {
+            init_sentinels_done = 0;
+        }
 
         /* Meeting point for all threads (wait for initialization) */
         pthread_mutex_lock(&gs.count_threads_mutex);
@@ -380,7 +383,7 @@ Py_set_num_threads(PyObject *self, PyObject *args)
 }
 
 static PyObject*
-Py_get_num_threads(PyObject *self, PyObject *args) 
+Py_get_num_threads(PyObject *self, PyObject *args)
 {
     int n_thread;
     n_thread = gs.nthreads;
@@ -477,6 +480,10 @@ PyInit_interpreter(void) {
     if (m == NULL)
         INITERROR;
 
+    #ifdef Py_GIL_DISABLED
+        PyUnstable_Module_SetGIL(m, Py_MOD_GIL_NOT_USED);
+    #endif
+
     Py_INCREF(&NumExprType);
     PyModule_AddObject(m, "NumExpr", (PyObject *)&NumExprType);
 
diff --git a/numexpr/necompiler.py b/numexpr/necompiler.py
index 98aee4c..296c41b 100644
--- a/numexpr/necompiler.py
+++ b/numexpr/necompiler.py
@@ -774,9 +774,12 @@ def getArguments(names, local_dict=None, global_dict=None, _frame_depth: int=2):
 
 
 # Dictionaries for caching variable names and compiled expressions
-_names_cache = CacheDict(256)
-_numexpr_cache = CacheDict(256)
-_numexpr_last = ContextDict()
+# _names_cache = CacheDict(256)
+_names_cache = threading.local()
+# _numexpr_cache = CacheDict(256)
+_numexpr_cache = threading.local()
+# _numexpr_last = ContextDict()
+_numexpr_last = threading.local()
 evaluate_lock = threading.Lock()
 
 def validate(ex: str, 
@@ -853,6 +856,14 @@ def validate(ex: str,
     
     """
     global _numexpr_last
+    if not hasattr(_numexpr_last, 'l'):
+        _numexpr_last.l = ContextDict()
+
+    if not hasattr(_names_cache, 'c'):
+        _names_cache.c = CacheDict(256)
+
+    if not hasattr(_numexpr_cache, 'c'):
+        _numexpr_cache.c = CacheDict(256)
 
     try:
         
@@ -868,9 +879,9 @@ def validate(ex: str,
         # Get the names for this expression
         context = getContext(kwargs)
         expr_key = (ex, tuple(sorted(context.items())))
-        if expr_key not in _names_cache:
-            _names_cache[expr_key] = getExprNames(ex, context, sanitize=sanitize)
-        names, ex_uses_vml = _names_cache[expr_key]
+        if expr_key not in _names_cache.c:
+            _names_cache.c[expr_key] = getExprNames(ex, context, sanitize=sanitize)
+        names, ex_uses_vml = _names_cache.c[expr_key]
         arguments = getArguments(names, local_dict, global_dict, _frame_depth=_frame_depth)
 
         # Create a signature
@@ -880,12 +891,12 @@ def validate(ex: str,
         # Look up numexpr if possible.
         numexpr_key = expr_key + (tuple(signature),)
         try:
-            compiled_ex = _numexpr_cache[numexpr_key]
+            compiled_ex = _numexpr_cache.c[numexpr_key]
         except KeyError:
-            compiled_ex = _numexpr_cache[numexpr_key] = NumExpr(ex, signature, sanitize=sanitize, **context)
+            compiled_ex = _numexpr_cache.c[numexpr_key] = NumExpr(ex, signature, sanitize=sanitize, **context)
         kwargs = {'out': out, 'order': order, 'casting': casting,
                   'ex_uses_vml': ex_uses_vml}
-        _numexpr_last.set(ex=compiled_ex, argnames=names, kwargs=kwargs)
+        _numexpr_last.l.set(ex=compiled_ex, argnames=names, kwargs=kwargs)
     except Exception as e:
         return e
     return None
@@ -987,13 +998,15 @@ def re_evaluate(local_dict: Optional[Dict] = None,
         not set this value.
     """
     global _numexpr_last
+    if not hasattr(_numexpr_last, 'l'):
+        _numexpr_last.l = ContextDict()
 
     try:
-        compiled_ex = _numexpr_last['ex']
+        compiled_ex = _numexpr_last.l['ex']
     except KeyError:
         raise RuntimeError("A previous evaluate() execution was not found, please call `validate` or `evaluate` once before `re_evaluate`")
-    argnames = _numexpr_last['argnames']
+    argnames = _numexpr_last.l['argnames']
     args = getArguments(argnames, local_dict, global_dict, _frame_depth=_frame_depth)
-    kwargs = _numexpr_last['kwargs']
+    kwargs = _numexpr_last.l['kwargs']
     with evaluate_lock:
         return compiled_ex(*args, **kwargs)
diff --git a/numexpr/tests/test_numexpr.py b/numexpr/tests/test_numexpr.py
index 62210b4..98ae459 100644
--- a/numexpr/tests/test_numexpr.py
+++ b/numexpr/tests/test_numexpr.py
@@ -36,6 +36,13 @@
 from numexpr.utils import detect_number_of_cores
 
 import unittest
+from unittest.mock import MagicMock
+
+try:
+    import pytest
+    pytest_available = True
+except ImportError:
+    pytest_available = False
 
 TestCase = unittest.TestCase
 
@@ -44,6 +51,15 @@
 MAX_THREADS = 16
 
 
+if not pytest_available:
+    def identity(f):
+        return f
+
+    pytest = MagicMock()
+    pytest.mark = MagicMock()
+    pytest.mark.thread_unsafe = identity
+
+
 class test_numexpr(TestCase):
     """Testing with 1 thread"""
     nthreads = 1
@@ -318,6 +334,7 @@ def test_refcount(self):
         evaluate('1')
         assert sys.getrefcount(a) == 2
 
+    @pytest.mark.thread_unsafe
     def test_locals_clears_globals(self):
         # Check for issue #313, whereby clearing f_locals also clear f_globals
         # if in the top-frame. This cannot be done inside `unittest` as it is always
@@ -341,6 +358,7 @@ def test_locals_clears_globals(self):
 
 
 
+@pytest.mark.thread_unsafe
 class test_numexpr2(test_numexpr):
     """Testing with 2 threads"""
     nthreads = 2
@@ -512,6 +530,7 @@ def test_illegal_value(self):
         else:
             self.fail()
 
+    @pytest.mark.thread_unsafe
     def test_sanitize(self):
         with _environment('NUMEXPR_SANITIZE', '1'):
             # Forbid dunder
@@ -590,7 +609,7 @@ def test_sanitize(self):
             x = np.array(['a', 'b'], dtype=bytes)
             evaluate("x == 'b:'")
 
-
+    @pytest.mark.thread_unsafe
     def test_no_sanitize(self):
         try: # Errors on compile() after eval()
             evaluate('import os;', sanitize=False)
@@ -677,6 +696,7 @@ def test_ex_uses_vml(self):
     if 'sparc' not in platform.machine():
         # Execution order set here so as to not use too many threads
         # during the rest of the execution.  See #33 for details.
+        @pytest.mark.thread_unsafe
         def test_changing_nthreads_00_inc(self):
             a = linspace(-1, 1, 1000000)
             b = ((.25 * a + .75) * a - 1.5) * a - 2
@@ -685,6 +705,7 @@ def test_changing_nthreads_00_inc(self):
                 c = evaluate("((.25*a + .75)*a - 1.5)*a - 2")
                 assert_array_almost_equal(b, c)
 
+        @pytest.mark.thread_unsafe
         def test_changing_nthreads_01_dec(self):
             a = linspace(-1, 1, 1000000)
             b = ((.25 * a + .75) * a - 1.5) * a - 2
@@ -1123,6 +1144,7 @@ def _environment(key, value):
             del os.environ[key]
 
 # Test cases for the threading configuration
+@pytest.mark.thread_unsafe
 class test_threading_config(TestCase):
     def test_max_threads_unset(self):
         # Has to be done in a subprocess as `importlib.reload` doesn't let us
@@ -1306,6 +1328,7 @@ def _worker(qout=None):
 
 # Case test for subprocesses (via multiprocessing module)
 class test_subprocess(TestCase):
+    @pytest.mark.thread_unsafe
     def test_multiprocess(self):
         try:
             import multiprocessing as mp