Mudder may refer to:
A participant in: Mud bogging, a form of off-road motorsport Multi-user dungeon, an online game Obstacle course racing, a sport in which competitors on foot must overcome obstacles including mud Tough Mudder, an endurance event series A racehorse that performs well on muddy or wet tracks A character in "Jaynestown", an episode of the science fiction television series Firefly Marian Mudder, Dutch actor and author