diff --git a/gnu/packages/patches/python-optree-fix-32-bit.patch b/gnu/packages/patches/python-optree-fix-32-bit.patch
new file mode 100644
index 0000000000..6a32c39bd8
--- /dev/null
+++ b/gnu/packages/patches/python-optree-fix-32-bit.patch
@@ -0,0 +1,122 @@
+In include/utils.h, ssize_t is an alias for py::ssize_t, which is an alias for
+Py_ssize_t in Python, which is an alias for the system ssize_t.
+The latter is defined in glibc as int if __WORDSIZE == 32 and as long int if
+__WORDSIZE == 64.  Therefore, we need to remove the explicit template
+specialization for int in the first case.
+
+diff --git a/include/utils.h b/include/utils.h
+index 950a02b..82a9591 100644
+--- a/include/utils.h
++++ b/include/utils.h
+@@ -141,10 +141,12 @@ template <>
+ inline py::handle GET_ITEM_HANDLE<py::tuple>(const py::handle& container, const size_t& item) {
+     return PyTuple_GET_ITEM(container.ptr(), py::ssize_t_cast(item));
+ }
++#if __WORDSIZE != 32
+ template <>
+ inline py::handle GET_ITEM_HANDLE<py::tuple>(const py::handle& container, const int& item) {
+     return PyTuple_GET_ITEM(container.ptr(), py::ssize_t_cast(item));
+ }
++#endif
+ template <>
+ inline py::handle GET_ITEM_HANDLE<py::list>(const py::handle& container, const ssize_t& item) {
+     return PyList_GET_ITEM(container.ptr(), item);
+@@ -153,10 +155,12 @@ template <>
+ inline py::handle GET_ITEM_HANDLE<py::list>(const py::handle& container, const size_t& item) {
+     return PyList_GET_ITEM(container.ptr(), py::ssize_t_cast(item));
+ }
++#if __WORDSIZE != 32
+ template <>
+ inline py::handle GET_ITEM_HANDLE<py::list>(const py::handle& container, const int& item) {
+     return PyList_GET_ITEM(container.ptr(), py::ssize_t_cast(item));
+ }
++#endif
+ 
+ template <typename Container, typename Item>
+ inline py::object GET_ITEM_BORROW(const py::handle& container, const Item& item) {
+@@ -171,11 +175,13 @@ inline py::object GET_ITEM_BORROW<py::tuple>(const py::handle& container, const
+     return py::reinterpret_borrow<py::object>(
+         PyTuple_GET_ITEM(container.ptr(), py::ssize_t_cast(item)));
+ }
++#if __WORDSIZE != 32
+ template <>
+ inline py::object GET_ITEM_BORROW<py::tuple>(const py::handle& container, const int& item) {
+     return py::reinterpret_borrow<py::object>(
+         PyTuple_GET_ITEM(container.ptr(), py::ssize_t_cast(item)));
+ }
++#endif
+ template <>
+ inline py::object GET_ITEM_BORROW<py::list>(const py::handle& container, const ssize_t& item) {
+     return py::reinterpret_borrow<py::object>(PyList_GET_ITEM(container.ptr(), item));
+@@ -185,11 +191,13 @@ inline py::object GET_ITEM_BORROW<py::list>(const py::handle& container, const s
+     return py::reinterpret_borrow<py::object>(
+         PyList_GET_ITEM(container.ptr(), py::ssize_t_cast(item)));
+ }
++#if __WORDSIZE != 32
+ template <>
+ inline py::object GET_ITEM_BORROW<py::list>(const py::handle& container, const int& item) {
+     return py::reinterpret_borrow<py::object>(
+         PyList_GET_ITEM(container.ptr(), py::ssize_t_cast(item)));
+ }
++#endif
+ 
+ template <typename Container, typename Item>
+ inline py::object GET_ITEM_STEAL(const py::handle& container, const Item& item) {
+@@ -204,11 +212,13 @@ inline py::object GET_ITEM_STEAL<py::tuple>(const py::handle& container, const s
+     return py::reinterpret_steal<py::object>(
+         PyTuple_GET_ITEM(container.ptr(), py::ssize_t_cast(item)));
+ }
++#if __WORDSIZE != 32
+ template <>
+ inline py::object GET_ITEM_STEAL<py::tuple>(const py::handle& container, const int& item) {
+     return py::reinterpret_steal<py::object>(
+         PyTuple_GET_ITEM(container.ptr(), py::ssize_t_cast(item)));
+ }
++#endif
+ template <>
+ inline py::object GET_ITEM_STEAL<py::list>(const py::handle& container, const ssize_t& item) {
+     return py::reinterpret_steal<py::object>(PyList_GET_ITEM(container.ptr(), item));
+@@ -218,11 +228,13 @@ inline py::object GET_ITEM_STEAL<py::list>(const py::handle& container, const si
+     return py::reinterpret_steal<py::object>(
+         PyList_GET_ITEM(container.ptr(), py::ssize_t_cast(item)));
+ }
++#if __WORDSIZE != 32
+ template <>
+ inline py::object GET_ITEM_STEAL<py::list>(const py::handle& container, const int& item) {
+     return py::reinterpret_steal<py::object>(
+         PyList_GET_ITEM(container.ptr(), py::ssize_t_cast(item)));
+ }
++#endif
+ 
+ template <typename Container, typename Item>
+ inline void SET_ITEM(const py::handle& container, const Item& item, const py::handle& value) {
+@@ -240,12 +252,14 @@ inline void SET_ITEM<py::tuple>(const py::handle& container,
+                                 const py::handle& value) {
+     PyTuple_SET_ITEM(container.ptr(), py::ssize_t_cast(item), value.inc_ref().ptr());
+ }
++#if __WORDSIZE != 32
+ template <>
+ inline void SET_ITEM<py::tuple>(const py::handle& container,
+                                 const int& item,
+                                 const py::handle& value) {
+     PyTuple_SET_ITEM(container.ptr(), py::ssize_t_cast(item), value.inc_ref().ptr());
+ }
++#endif
+ template <>
+ inline void SET_ITEM<py::list>(const py::handle& container,
+                                const ssize_t& item,
+@@ -258,12 +272,14 @@ inline void SET_ITEM<py::list>(const py::handle& container,
+                                const py::handle& value) {
+     PyList_SET_ITEM(container.ptr(), py::ssize_t_cast(item), value.inc_ref().ptr());
+ }
++#if __WORDSIZE != 32
+ template <>
+ inline void SET_ITEM<py::list>(const py::handle& container,
+                                const int& item,
+                                const py::handle& value) {
+     PyList_SET_ITEM(container.ptr(), py::ssize_t_cast(item), value.inc_ref().ptr());
+ }
++#endif
+ 
+ template <typename PyType>
+ inline void AssertExact(const py::handle& object) {
diff --git a/gnu/packages/python-xyz.scm b/gnu/packages/python-xyz.scm
index 0c72caeca0..b664aac3b7 100644
--- a/gnu/packages/python-xyz.scm
+++ b/gnu/packages/python-xyz.scm
@@ -148,6 +148,7 @@
 ;;; Copyright © 2023, 2024 Troy Figiel <troy@troyfigiel.com>
 ;;; Copyright © 2024 Timothee Mathieu <timothee.mathieu@inria.fr>
 ;;; Copyright © 2024 Ian Eure <ian@retrospec.tv>
+;;; Copyright © 2024 David Elsing <david.elsing@posteo.net>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -11636,6 +11637,35 @@ (define-public python-treelib
      "This package provides a Python implementation of a tree structure.")
     (license license:asl2.0)))
 
+(define-public python-optree
+  (package
+    (name "python-optree")
+    (version "0.10.0")
+    (source
+     (origin
+       (method git-fetch)
+       (uri (git-reference
+             (url "https://github.com/metaopt/optree")
+             (commit (string-append "v" version))))
+       (file-name (git-file-name name version))
+       (sha256
+        (base32
+         "1q3wljk7cyl5rsam02sfsj8zjrqx4c3x9vic8j6xx13p8czpsisg"))
+       (patches (search-patches "python-optree-fix-32-bit.patch"))))
+    (build-system pyproject-build-system)
+    (propagated-inputs (list python-typing-extensions))
+    (native-inputs
+     (list python-pytest
+           python-pytest-cov
+           python-pytest-xdist
+           cmake
+           pybind11))
+    (home-page "https://github.com/metaopt/optree")
+    (synopsis "Optimized PyTree Utilities")
+    (description "This package contains operations on PyTrees (a tree made of
+container data structures in Python).")
+    (license license:asl2.0)))
+
 (define-public python-jupyter-core
   (package
     (name "python-jupyter-core")
