Antichess

Captures are mandatory. Lose all your pieces to win. Inverts the entire logic of chess.

Antichess — starting position

Setup

Board: Standard 8×8.

Setup: Standard chess setup.

FEN: rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1

Rules

If a capture is available, you MUST capture. If multiple captures are available, you may choose which one.
The King has no royal status — it can be captured like any other piece and there is no check or checkmate.
No castling.
Pawns may promote to King (in addition to the usual pieces).
Stalemate (no legal moves) is a WIN for the stalemated player.

Win Condition

Lose all your pieces, or be stalemated.

Strategy

You want to force your opponent to capture your pieces while avoiding being forced to keep yours. Opening theory is highly developed — certain openings force wins within a few moves.

Attribution

Also known as “Losing Chess,” “Giveaway Chess,” or “Suicide Chess.” Traditional variant, 19th century. Public domain.