In the sport of baseball, a doubleheader is a set of two games played between the same two teams on the same day. Historically, doubleheaders have been played in immediate succession, in front of the same crowd. Contemporarily, the term is also used to refer to two games played between two teams in a single day in front of different crowds and not in immediate succession.

The record for the most doubleheaders played by a major-league team in one season is 44 by the 1943 Chicago White Sox.