A straw man fallacy (sometimes written as strawman) is the informal fallacy of refuting an argument different from the one actually under discussion, while not recognizing or acknowledging the distinction. One who engages in this fallacy is said to be "attacking a straw man".

The typical straw man argument creates the illusion of having refuted or defeated an opponent's proposition through the covert replacement of it with a different proposition (i.e., "stand up a straw man") and the subsequent refutation of that false argument ("knock down a straw man") instead of the opponent's proposition.