Emil John "Dutch" Leonard (March 25, 1909 – April 17, 1983) was an American professional baseball player.

He played in Major League Baseball (MLB) as a right-handed knuckleball pitcher for the Brooklyn Dodgers (1933–1936), Washington Senators (1938–1946), Philadelphia Phillies (1947–1948) and Chicago Cubs (1949–1953).

Born in Auburn, Illinois, Leonard batted right-handed and was listed as 6 feet (1.8 m) tall and 175 pounds (79 kg).

At a ceremony between that game and the nightcap, Lou Gehrig, who had recently been diagnosed with ALS, delivered his famous "luckiest man on the face of the earth" speech.

During Washington's 1945 season, Leonard was part of what was possibly the only four-man rotation in baseball history to have been all knuckleball pitchers, joining Mickey Haefner, Johnny Niggeling and Roger Wolff.