diff --git a/changes/+c563f4d4.bugfix.rst b/changes/+c563f4d4.bugfix.rst
new file mode 100644
index 0000000000..6f9fedaa46
--- /dev/null
+++ b/changes/+c563f4d4.bugfix.rst
@@ -0,0 +1 @@
+Register 'gpu' marker with pytest for downstream StoreTests.
diff --git a/pyproject.toml b/pyproject.toml
index 85517d8d0a..102ee76df6 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -138,6 +138,7 @@ exclude_lines = [
 [tool.coverage.run]
 omit = [
     "bench/compress_normal.py",
+    "src/zarr/testing/conftest.py",  # only for downstream projects
 ]
 
 [tool.hatch]
@@ -455,3 +456,6 @@ issue_format = ":issue:`{issue}`"
 
 [tool.codespell]
 ignore-words-list = "astroid"
+
+[project.entry-points.pytest11]
+zarr = "zarr.testing"
diff --git a/src/zarr/testing/conftest.py b/src/zarr/testing/conftest.py
new file mode 100644
index 0000000000..59c148e0ec
--- /dev/null
+++ b/src/zarr/testing/conftest.py
@@ -0,0 +1,9 @@
+import pytest
+
+
+def pytest_configure(config: pytest.Config) -> None:
+    # The tests in zarr.testing are intended to be run by downstream projects.
+    # To allow those downstream projects to run with `--strict-markers`, we need
+    # to register an entry point with pytest11 and register our "plugin" with it,
+    # which just registers the markers used in zarr.testing
+    config.addinivalue_line("markers", "gpu: mark a test as requiring CuPy and GPU")