Kenesaw Mountain Landis (; November 20, 1866 – November 25, 1944) was an American jurist who served as a United States federal judge from 1905 to 1922 and the first Commissioner of Baseball from 1920 until his death. He is remembered for his handling of the Black Sox Scandal, in which he expelled eight members of the Chicago White Sox from organized baseball for conspiring to lose the 1919 World Series and repeatedly refused their reinstatement requests. His firm actions and iron rule over baseball in the near quarter-century of his commissionership are generally credited with restoring public confidence in the game.

Landis was born in Millville, Ohio. His given name was a variant spelling of the site of the Battle of Kennesaw Mountain, a major battle of the American Civil War in which his father had been wounded. Raised in Indiana, Landis became a lawyer, and then personal secretary to Walter Q. Gresham, the new United States Secretary of State, in 1893. He returned to private practice after Gresham died in office.

President Theodore Roosevelt appointed Landis as a judge of the United States District Court for the Northern District of Illinois in 1905. Landis received national attention in 1907 when he fined Standard Oil of Indiana more than $29 million (approximately $800 million in 2021) for violating federal laws forbidding rebates on railroad freight tariffs. While Landis's action was reversed on appeal, he was seen as a judge determined to rein in big business. During and after World War I, Landis presided over several high-profile trials of draft resisters and others whom he saw as opposing the war effort. He imposed heavy sentences on those who were convicted, although some of the convictions were reversed on appeal, and other sentences were commuted.

In 1920, Landis was a leading candidate when American League and National League team owners, embarrassed by the Black Sox scandal and other instances of players throwing games, sought someone to rule over baseball. Landis was given full power to act in the sport's best interest, and used that power extensively over the next quarter-century. Landis was widely praised for cleaning up the game, although some of his decisions in the Black Sox matter remain controversial: supporters of "Shoeless Joe" Jackson and Buck Weaver contend that he was overly harsh with those players. Others blame Landis for, in their view, delaying the racial integration of baseball. Landis was elected to the National Baseball Hall of Fame by a special vote shortly after he died in 1944.