diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 9c218399f..e642299f1 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -130,7 +130,7 @@ jobs:
       - name: Run pytest
         run: |
           echo '::add-matcher::.github/problem-matchers/pytest.json'
-          check/pytest -n auto -m "not slow"
+          check/pytest -n auto --skipslow
 
   pytest-extra:
     name: Extra unit tests
@@ -162,7 +162,7 @@ jobs:
       - name: Run pytest
         run: |
           echo '::add-matcher::.github/problem-matchers/pytest.json'
-          check/pytest -n auto -m "not slow" src/openfermion/resource_estimates
+          check/pytest -n auto --skipslow src/openfermion/resource_estimates
 
   pytest-compat:
     name: Python compatibility tests
@@ -190,7 +190,7 @@ jobs:
       - name: Run pytest
         run: |
           echo '::add-matcher::.github/problem-matchers/pytest.json'
-          check/pytest -n auto -m "not slow"
+          check/pytest -n auto --skipslow
 
   coverage:
     name: Python code coverage tests
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index e4b603e49..3db515805 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -293,7 +293,7 @@ We use [pytest](https://docs.pytest.org) to run our tests and
 in the `check/` subdirectory to run these programs.
 
 *   During development, periodically check that code changes do not break anything. For fast checks,
-    run `check/pytest -m "not slow" -n auto PATH ...`, where `PATH ...` is one or more directories
+    run `check/pytest --skipslow -n auto PATH ...`, where `PATH ...` is one or more directories
     or `_test.py` files to test. (The `-n auto` option makes pytest use parallel processes; omit it
     if it causes problems on your system.)
 
diff --git a/conftest.py b/conftest.py
index 080bcba9d..3e50ce02f 100644
--- a/conftest.py
+++ b/conftest.py
@@ -66,3 +66,12 @@ def set_threadpool_limits():
             yield
     else:
         yield
+
+
+def pytest_addoption(parser: pytest.Parser) -> None:
+    parser.addoption("--skipslow", action="store_true", help="skips slow tests")
+
+
+def pytest_runtest_setup(item: pytest.Item) -> None:
+    if "slow" in item.keywords and item.config.getoption("skipslow"):
+        pytest.skip("skipped because of --skipslow option")
diff --git a/pyproject.toml b/pyproject.toml
index 72ba61d15..b8aa9b48a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -25,7 +25,7 @@ disable_warnings = ["no-sysmon"]
 
 [tool.pytest.ini_options]
 markers = [
-    """slow: marks tests as slow (deselect with '-m "not slow"')""",
+    """slow: marks tests as slow (skip with '--skipslow')""",
 ]
 filterwarnings = [
     "ignore:Skipped assert_qasm_is_consistent_with_unitary because qiskit.*:UserWarning",
diff --git a/src/openfermion/config_test.py b/src/openfermion/config_test.py
index c0fd7f79f..111f90411 100644
--- a/src/openfermion/config_test.py
+++ b/src/openfermion/config_test.py
@@ -170,3 +170,50 @@ def test_set_threading_limits(self):
             with patch("openfermion.config.get_available_cpu_count", return_value=8):
                 set_threading_limits()
                 self.assertEqual(os.environ.get("OMP_NUM_THREADS"), "7")
+
+
+class ConftestTest(unittest.TestCase):
+
+    def test_pytest_addoption(self):
+        import conftest
+        from unittest.mock import MagicMock
+
+        parser = MagicMock()
+        conftest.pytest_addoption(parser)
+        parser.addoption.assert_called_once_with(
+            "--skipslow", action="store_true", help="skips slow tests"
+        )
+
+    def test_pytest_runtest_setup_skips(self):
+        import conftest
+        import pytest
+        from unittest.mock import MagicMock
+
+        # Create mock item representing a slow test when skipslow is True.
+        item = MagicMock()
+        item.keywords = {"slow"}
+        item.config.getoption.return_value = True
+
+        with self.assertRaises(pytest.skip.Exception):
+            conftest.pytest_runtest_setup(item)
+
+        item.config.getoption.assert_called_once_with("skipslow")
+
+    def test_pytest_runtest_setup_does_not_skip_if_not_slow(self):
+        import conftest
+        from unittest.mock import MagicMock
+
+        # Test case 1: Not marked as 'slow', skipslow is True.
+        item = MagicMock()
+        item.keywords = set()
+        item.config.getoption.return_value = True
+
+        # Should not raise an exception.
+        conftest.pytest_runtest_setup(item)
+
+        # Test case 2: Marked as 'slow', skipslow is False.
+        item = MagicMock()
+        item.keywords = {"slow"}
+        item.config.getoption.return_value = False
+
+        conftest.pytest_runtest_setup(item)