In chess, a "brilliancy" is an extremely strong move, often an unexpected or atypical move, which drastically improves a player's situation in a single move.

In chess notation, a move considered to be a "brilliancy" is typically marked with a double exclamation points (!!) after the move notation.

Players who play a game with one or more brilliancies in a tournament often win a special commendation called a "brilliancy prize."