was the first player to achieve 18 strikeouts in a game during the 20th century. was the first pitcher to achieve multiple games with 18 strikeouts, recording two in his career.|alt=A smiling man in a white baseball jersey and dark baseball cap with an interlocked white "LA" on the front. tied Roger Clemens' major league record of 20 strikeouts in a nine-inning game on May 6, 1998.|alt=A man sporting a goatee and wearing a dark blue baseball cap with "C" in the middle, a pinstriped jersey and black Nike cleats delivers a pitch. tied Kerry Wood and Roger Clemens' major league record of 20 strikeouts in a nine-inning game in 2016.|alt=A man in white pants and a navy blue baseball jersey with "Nationals" written across the front throws a pitch.
MLB pitchers with 18 strikeouts in a nine-inning game 18 strikeouts in extra-inning games amassed 18 or more strikeouts in a nine-inning game twice, as well as 19 strikeouts in extra-inning games three times.|alt=A man in a white baseball jersey with "ASTROS" on the chest and orange and yellow stripes on his shoulders pitches a baseball with his right hand. Eight different pitchers have struck out at least 18 batters in an
extra-inning Major League Baseball (MLB) game to date. Only
Nolan Ryan accomplished the feat more than once in his career and no player has ever struck out more than 21 batters in a game. The following list is kept separate from the above list of pitchers who have struck out 18 or more batters in a nine-inning game. This is due to the differing number of
innings pitched during an extra-inning game, the lack of a definitive endpoint to the game that would otherwise allow for a fair comparison to be made, and the advantage of having more opportunities to strike out players during an extra-inning game as opposed to one lasting nine innings. ==See also==