A bracket or tournament bracket is a tree diagram that represents the series of games played during a knockout tournament. Different knockout tournament formats have different brackets; the simplest and most common is that of the single-elimination tournament. The name "bracket" is American English, derived from the resemblance of the links in the tree diagram to the bracket punctuation symbol ] or [ (called a "square bracket" in British English). The closest British term is draw, although this implies an element of chance, whereas some brackets are determined entirely by seeding.

In some tournaments, the full bracket is determined before the first match. In such cases, fans may enjoy trying to predict the winners of the initial round and of the consequent later matchups. This is called "bracketology", particularly in relation to the NCAA Division I men's basketball tournament. This prediction is not possible in tournaments, such as the FA Cup and the UEFA Champions League knockout phase, in which the pairings for a later round might not be made until after the previous round has been played (UEFA Champions League makes its ultimate bracket draw at the quarterfinal stage ).