In chess, fool's mate is the checkmate delivered after the fewest possible moves from the game's starting position.

Fool's mate received its name because it can occur only if White commits an extraordinary blunder.

The mate is an illustration of the kingside weakness shared by both players along the f- and g-files during the opening phase of the game.

A player may also suffer an early checkmate if the f- and g-pawns are advanced prematurely and the kingside is not properly defended, as shown in historical miniature games recorded in chess literature.

Fool's mate was named and described in The Royal Game of Chess-Play, a 1656 text by Francis Beale that adapted the work of the early chess writer Gioachino Greco.

When the roles are reversed, however, White requires an extra third turn or half-move, known in computer chess as a ply.

In both cases, the principle is the same: a player advances their f- and g-pawns such that the opponent's queen can mate along the unblocked diagonal.

[5] The solution in Fischer's book bore the comment "Black foolishly weakened his King's defenses.

A well-known trap in the Dutch Defence occurred in the game Frank Melville Teed–Eugene Delmar, 1896:[13][14] It seems that Black has won the bishop, but now comes ...

Defending against Bg6#, but ... White sacrifices his queen to draw the black rook away from its control of g6.