代打(Pinch Hitter)，为一棒球调度术语，指棒球比赛中，可用来进行现有打击顺序名单替换的未上场球员，由于棒球规则规定，球员在退场后即不得再上场，因此代打者在下一局起就必须接续原球员的守备位置，若代打者的守备位置与原打者有异，则下一局起，防守阵容将会进行较大的变动。有指定打击的名单中，任何打者代打，皆直接入替原打者的位置，指定打击亦是直接入替。在九人制棒球中，除非教练团派另一投手代打，或该代打者被教练团要求下一局进行投球，否则在守备局，教练团必须另外一位投手接替上一任投手的投球。

In baseball, a pinch hitter is a substitute batter. Batters can be substituted at any time while the ball is dead (not in active play); the manager may use any player who has not yet entered the game as a substitute. Unlike basketball, American football, or ice hockey, baseball does not have a "free substitution rule" and thus the replaced player in baseball is never allowed back into that game. The pinch hitter assumes the spot in the batting order of the player whom he or she replaces.