diff --git a/tests/cancun/eip4788_beacon_root/conftest.py b/tests/cancun/eip4788_beacon_root/conftest.py
index a60e814c4ea..0c2ae2c1710 100644
--- a/tests/cancun/eip4788_beacon_root/conftest.py
+++ b/tests/cancun/eip4788_beacon_root/conftest.py
@@ -26,6 +26,13 @@
 BLOB_COMMITMENT_VERSION_KZG = 1
 
 
+def pytest_generate_tests(metafunc: pytest.Metafunc) -> None:
+    """Mark all tests in this subdir as not valid for Monad forks."""
+    metafunc.definition.add_marker(
+        pytest.mark.not_valid_for("MONAD_EIGHT", subsequent_forks=True)
+    )
+
+
 @pytest.fixture
 def timestamp() -> int:  # noqa: D103
     return 12
diff --git a/tests/osaka/eip7825_transaction_gas_limit_cap/test_tx_gas_limit.py b/tests/osaka/eip7825_transaction_gas_limit_cap/test_tx_gas_limit.py
index 98e665bf6fd..9ee868fa582 100644
--- a/tests/osaka/eip7825_transaction_gas_limit_cap/test_tx_gas_limit.py
+++ b/tests/osaka/eip7825_transaction_gas_limit_cap/test_tx_gas_limit.py
@@ -343,7 +343,22 @@ def total_cost_floor_per_token(fork: Fork) -> int:
         pytest.param(False, True),
     ],
 )
-@pytest.mark.parametrize("zero_byte", [True, False])
+@pytest.mark.parametrize(
+    "zero_byte",
+    [
+        pytest.param(
+            True,
+            marks=pytest.mark.monad_runloop(
+                pytest.mark.skip(
+                    reason="Filling the tx gas limit cap with zero bytes "
+                    "takes a ~3 MB tx, over the runloop 2 MB proposal "
+                    "byte limit."
+                )
+            ),
+        ),
+        False,
+    ],
+)
 # Osaka originally, but Monad introduces tx gas limit cap differently
 @pytest.mark.valid_from("MONAD_EIGHT")
 @pytest.mark.json_loader
diff --git a/tests/shanghai/eip4895_withdrawals/conftest.py b/tests/shanghai/eip4895_withdrawals/conftest.py
index 12707c2838f..e2b910cedd3 100644
--- a/tests/shanghai/eip4895_withdrawals/conftest.py
+++ b/tests/shanghai/eip4895_withdrawals/conftest.py
@@ -4,6 +4,13 @@
 from execution_testing import Alloc, Environment
 
 
+def pytest_generate_tests(metafunc: pytest.Metafunc) -> None:
+    """Mark all tests in this subdir as not valid for Monad forks."""
+    metafunc.definition.add_marker(
+        pytest.mark.not_valid_for("MONAD_EIGHT", subsequent_forks=True)
+    )
+
+
 @pytest.fixture
 def env() -> Environment:
     """Environment fixture."""