In baseball, a strikeout occurs when a pitcher throws three strikes to a batter during his time at bat.^[1] Twenty different pitchers have struck out at least 18 batters in a single nine-inning Major League Baseball (MLB) game,^{[lower-alpha 1]} the most recent being Max Scherzer of the Washington Nationals on May 11, 2016.^[4] Four players have accomplished the feat more than once in their career; no player has ever struck out more than 20 batters in a nine-inning game. Charlie Sweeney was the first player to strike out 18 batters in a single game, doing so for the Providence Grays against the Boston Beaneaters on June 7, 1884.^[5] In spite of this, Bob Feller is viewed as the first pitcher to accomplish the feat,^[6][7] since his then-record 18 strikeouts was the first to occur during the 20th century and the live-ball era.^[8]

Out of the twenty pitchers who have accomplished the feat, fifteen were right-handed and five pitched left-handed. Five of these players have played for only one major league team. Six pitchers—Steve Carlton, Roger Clemens, Randy Johnson, Nolan Ryan, Tom Seaver, and Max Scherzer—are also members of the 3,000 strikeout club. Sweeney has the fewest career strikeouts in the group with 505, while Nolan Ryan, with 5,714, struck out more batters than any other pitcher in major league history.^[9] Bill Gullickson and Kerry Wood are the only rookies to have achieved the feat.^[10][11] Tom Seaver concluded his milestone game by striking out the final ten batters he faced, setting a new major league record for most consecutive strikeouts.^[12][13]

Of the eleven players eligible for the Baseball Hall of Fame who have struck out 18 batters in a game, six have been elected; all six were elected on the first ballot.^[14] Players are eligible for the Hall of Fame if they have played in at least 10 major league seasons, and have either been retired for five seasons or deceased for at least six months.^[15]

• 3,000 strikeout club