Henry Louis Gehrig (born Heinrich Ludwig Gehrig; June 19, 1903 – June 2, 1941) was an American professional baseball first baseman who played 17 seasons in Major League Baseball (MLB) for the New York Yankees (1923–1939). Gehrig was renowned for his prowess as a hitter and for his durability, which earned him his nickname "The Iron Horse". He was an All-Star seven consecutive times, a Triple Crown winner once, an American League (AL) Most Valuable Player twice, and a member of six World Series champion teams. He had a career .340 batting average, .632 slugging average, and a .447 on base average. He hit 493 home runs and had 1,995 runs batted in (RBI). He still has the highest ratio of runs scored plus runs batted in per 100 plate appearances (35.08) and per 100 games (156.7) among Hall of Fame players. In 1939, he was elected to the Baseball Hall of Fame and was the first MLB player to have his uniform number (4) retired by a team.

A native of New York City and a student at Columbia University, Gehrig signed with the Yankees in 1923. He set several major-league records during his career, including the most career grand slams (23; since broken by Alex Rodriguez) and most consecutive games played (2,130), a record that stood for 56 years and was long considered unbreakable until surpassed by Cal Ripken Jr., in 1995. Gehrig's consecutive game streak ended on May 2, 1939, when he voluntarily took himself out of the lineup, stunning both players and fans, after his performance on the field became hampered by an undiagnosed ailment subsequently confirmed to be amyotrophic lateral sclerosis, an incurable neuromuscular illness; it is now commonly referred to in North America as "Lou Gehrig's disease".The disease forced him to retire at age 36, and claimed his life two years later. The pathos of his farewell from baseball was capped off by his iconic 1939 "Luckiest Man on the Face of the Earth" speech at Yankee Stadium.

In 1969, the Baseball Writers' Association of America voted Gehrig the greatest first baseman of all time, and he was the leading vote-getter on the MLB All-Century Team chosen by fans in 1999. A monument in Gehrig's honor, originally dedicated by the Yankees in 1941, currently resides in Monument Park at Yankee Stadium. The Lou Gehrig Memorial Award is given annually to the MLB player who best exhibits Gehrig's integrity and character.