The "cat hair mustache puzzle" is a colloquial name given to a puzzle in the 1999 adventure game Gabriel Knight 3: Blood of the Sacred, Blood of the Damned. The puzzle involves disguising the protagonist Gabriel Knight with hair from a cat, in order to steal a man's motorcycle rental. It was created by the game's producer, Steven Hill, after a puzzle designed by the game's lead designer, Jane Jensen, was cut due to budgetary reasons. The designers disliked the puzzle, but because of time constraints, it had to be left in.
The puzzle received generally negative reception. It has frequently been identified as one of the worst puzzles in the adventure game genre, with one writer going so far as to call it partly responsible for the decline in overall popularity of the genre.