List of Major League Baseball single-inning strikeout leaders

In baseball, a strikeout occurs when a pitcher throws three strikes to a batter during his time at bat. Under Rules 6.05 and 6.09 of the Official Rules of Major League Baseball, a batter becomes a runner when a third strike is not caught by the catcher with no runner on first base or when there are two outs. The strikeout is recorded, but the batter-runner must be tagged or forced out in order for the defensive team to register the out. Thus, it is possible for a pitcher to record more than three strikeouts in an inning. As a result of this rule, 71 different pitchers have struck out four batters in a half-inning of a Major League Baseball (MLB) game as of 2015^[update], the most recent being Jon Gray of the Colorado Rockies on September 17, 2016. Three players—Chuck Finley, A. J. Burnett and Zack Greinke—have accomplished the feat more than once in their career; no player has ever struck out more than four batters in an inning. Ed Crane was the first player to strike out four batters in one inning, doing so in the fifth inning for the New York Giants against the on October 4, 1888.