diff --git a/src/pf1e_simulator/combat.py b/src/pf1e_simulator/combat.py
index 1663f93..3e32c93 100644
--- a/src/pf1e_simulator/combat.py
+++ b/src/pf1e_simulator/combat.py
@@ -4097,6 +4097,11 @@ class CombatEngine:
         if self.has_condition_flag(state, "cant_move"):
             self._log(f"round {self._current_round} {state.combatant.id}: wait (cannot move)")
             return ActionResult(kind=kind, ok=True, reason=_REASON_OK)
+        # SRD "Conditions — Fatigued": "A fatigued character can neither run
+        # nor charge" (same for exhausted/entangled via cant_charge).
+        if self.has_condition_flag(state, "cant_charge"):
+            self._log(f"round {self._current_round} {state.combatant.id}: wait (cannot run)")
+            return ActionResult(kind=kind, ok=True, reason=_REASON_OK)
         if action.destination is not None:
             if action.destination == state.pos:
                 path: list[Pos] = []  # already there: a valid zero-length run
diff --git a/tests/test_conditions_effects.py b/tests/test_conditions_effects.py
index 762a271..73395a4 100644
--- a/tests/test_conditions_effects.py
+++ b/tests/test_conditions_effects.py
@@ -8,7 +8,14 @@ Part (b): Condition behavioral effects enforced via action economy / AC modifier
 from __future__ import annotations
 
 from pf1e_simulator.combat import Action, CombatantState, CombatEngine
-from pf1e_simulator.conditions import NAUSEATED, PARALYZED, PRONE, STAGGERED
+from pf1e_simulator.conditions import (
+    EXHAUSTED,
+    FATIGUED,
+    NAUSEATED,
+    PARALYZED,
+    PRONE,
+    STAGGERED,
+)
 from pf1e_simulator.dice import parse_dice
 from pf1e_simulator.effects import ActiveCondition, StatModifier
 from pf1e_simulator.grid import Grid
@@ -226,7 +233,76 @@ class TestStaggeredActionEconomy:
         assert h.pos != (10, 10)
 
 
-# ── Test 4: nauseated → single move action only ───────────────────────────────
+# ── Test 3b: fatigued/exhausted cannot run ────────────────────────────────────
+
+
+class TestFatiguedCannotRun:
+    """Given: a fatigued or exhausted combatant
+    When: the engine executes a run action
+    Then: the run is blocked (SRD: "A fatigued character can neither run nor
+    charge"; exhausted and entangled share the cant_charge flag)."""
+
+    def test_fatigued_cannot_run(self) -> None:
+        legend = {".": TerrainType(type="floor", move_cost=1)}
+        grid = Grid.from_spec(
+            MapSpec(name="big", terrain=tuple(["." * 20] * 20), legend=legend)
+        )
+        hero = _make_hero()
+        foe = _make_foe()
+        h = CombatantState(combatant=hero, side="players", pos=(0, 0), hp=hero.hp_max)
+        f = CombatantState(combatant=foe, side="monsters", pos=(10, 0), hp=foe.hp_max)
+        h.active_conditions.append(
+            ActiveCondition(condition=FATIGUED, rounds_left=5, source="test")
+        )
+        engine = CombatEngine(
+            ScriptedRng([10, 9]),
+            grid,
+            [h, f],
+            round_cap=1,
+            policy=lambda _e, s: (
+                (Action(kind="run", target_id="foe"),)
+                if s.combatant.id == hero.id
+                else (Action(kind="wait"),)
+            ),
+        )
+        engine.run()
+        run_lines = [
+            line for line in engine._transcript
+            if "hero: run" in line or "hero: wait" in line
+        ]
+        assert any("wait (cannot run)" in line for line in run_lines)
+        assert h.pos == (0, 0)
+
+    def test_exhausted_cannot_run(self) -> None:
+        legend = {".": TerrainType(type="floor", move_cost=1)}
+        grid = Grid.from_spec(
+            MapSpec(name="big", terrain=tuple(["." * 20] * 20), legend=legend)
+        )
+        hero = _make_hero()
+        foe = _make_foe()
+        h = CombatantState(combatant=hero, side="players", pos=(0, 0), hp=hero.hp_max)
+        f = CombatantState(combatant=foe, side="monsters", pos=(10, 0), hp=foe.hp_max)
+        h.active_conditions.append(
+            ActiveCondition(condition=EXHAUSTED, rounds_left=5, source="test")
+        )
+        engine = CombatEngine(
+            ScriptedRng([10, 9]),
+            grid,
+            [h, f],
+            round_cap=1,
+            policy=lambda _e, s: (
+                (Action(kind="run", target_id="foe"),)
+                if s.combatant.id == hero.id
+                else (Action(kind="wait"),)
+            ),
+        )
+        engine.run()
+        run_lines = [
+            line for line in engine._transcript
+            if "hero: run" in line or "hero: wait" in line
+        ]
+        assert any("wait (cannot run)" in line for line in run_lines)
+        assert h.pos == (0, 0)
 
 
 class TestNauseatedActionEconomy: