John Henry Neun (October 28, 1900 - March 28, 1990) was an American first baseman for the Detroit Tigers and the Boston Braves from to .

Although never an everyday player (he never played more than 97 games a season), Neun entered baseball immortality on May 31, against the Cleveland Indians, when he caught a line drive from Homer Summa, stepped on first to retire Charlie Jamieson, and despite shouts from his shortstop to throw him the ball, raced towards second base to retire Glenn Myatt, completing the seventh unassisted triple play in MLB history, and the first such play to end a game. That feat that would not be duplicated for 82 years, when on August 23, 2009, Eric Bruntlett turned an unassisted triple play for the Philadelphia Phillies to end a game against the New York Mets. More remarkably, Neun turned the triple play as a first baseman and not a second baseman or shortstop, and did so one day after Jimmy Cooney of the Chicago Cubs had done so. A switch-hitter who threw left-handed, Neun batted .289 with two home runs in 945 at bats during his seven-year Major League Baseball career.

In , after retiring as a player, Neun began managing in the New York Yankees' farm system, and from through , he piloted the AA Newark Bears, winning International League regular season championships in 1938 (104 wins) and 1941 (100 wins) and the 1938 playoff title. He then spent two seasons as skipper of the Yanks' other top affiliate, the Kansas City Blues of the American Association (where he won another regular-season pennant, in ), before joining the New York coaching staff in .

In September , he was hired as the manager of the Yankees, replacing Bill Dickey. His stint in New York lasted only 14 games (8-6) through the third-place Yankees' final regular season game. But during the offseason, he was hired by the Cincinnati Reds as the successor to Baseball Hall of Fame manager Bill McKechnie. Neun had subpar numbers in Cincinnati, going 117-137 in parts of two seasons. He was dismissed after 100 games in in favor of Bucky Walters. He continued working in the game, and into his 80s was a scout and instructor for the Milwaukee Brewers.

Neun died of pancreatic cancer in his birthplace of Baltimore, Maryland at age 89.

Rumors that Neun refusing to throw the ball to the shortstop were said by Jon Miller of ESPN with Miller saying Neun told the shortstop that he didn't throw the ball to him because he knew the ball was destined for the baseball hall of fame. The Baseball Hall of Fame was formed in 1939, twelve years after the feat making that story quite doubtful.