The shortest checkmate possible in chess is where black wins after two moves. In order for it to work, white needs to move their g-pawn to g4 on their first or second move, and black need only open a diagonal for the queen. From there, if white ever moves the f-pawn, queen h4 is checkmate. This is a 2-move mate also known as "The Fool's Mate". It is the fastest possible way to give checkmate in chess.