John Leonard Hopp (July 18, 1916 – June 1, 2003) was an American professional baseball player and coach.

Born in Hastings, Nebraska, he was an outfielder and first baseman who appeared in 1,393 Major League Baseball games over 14 seasons (1939–52) for the St. Louis Cardinals, Boston Braves, Pittsburgh Pirates, Brooklyn Dodgers, New York Yankees and Detroit Tigers.

Hopp made his Cardinal debut on September 18, 1939, and entered the big leagues for good the following season.

During his first season as a regular, 1941, Hopp started 75 games in the outfield and another 33 as backup first baseman to slugger Johnny Mize.

The last wartime season, 1945, saw Hopp become the Cardinals' regular right fielder, and his batting average fell to .289 as St. Louis finished second, three games behind the Chicago Cubs.

That off-season, Cardinal manager Billy Southworth moved to the Boston Braves, and with the surplus of major-league talent coming back from wartime service, Boston began purchasing players who had contributed to Southworth's successful Cardinal teams of 1940–45.

Selected to the 1946 National League All-Star team, Hopp started in center field at Fenway Park on July 9 and singled against Bob Feller in two at bats.

Hopp returned to the Braves in 1947, but was platooned in center field with right-handed-hitting Mike McCormick and his average fell to .288.

[4] The Yankees released Hopp in late May 1952 and he caught on days later with the Tigers, who had fallen all the way from pennant contention in 1950 to last place in 1952.

His last big-league manager, Fred Hutchinson, appointed Hopp to his coaching staff with the 1954 Tigers and 1956 Cardinals.