An eephus pitch in baseball is a very high-arcing off-speed pitch. The delivery from the pitcher has very low velocity and often catches the hitter off-guard. The eephus pitch is thrown overhand like most pitches, but is characterized by an unusual, high-arcing trajectory. The corresponding slow velocity bears more resemblance to a slow-pitch softball delivery than to a traditional baseball pitch. It is considered a trick pitch because, in comparison to normal baseball pitches, which run from 70 to 100 miles per hour, an eephus pitch appears to move in slow motion at 55 mph (89 km/h) or less, sometimes as low as 35 mph (56 km/h).

Theodore Samuel Williams was an American professional baseball player and manager. He played his entire 19-year Major League Baseball (MLB) career, primarily as a left fielder, for the Boston Red Sox from 1939 to 1960; his career was interrupted by military service during World War II and the Korean War. Nicknamed "Teddy Ballgame", "the Kid", "the Splendid Splinter", and "the Thumper", Williams is regarded as one of the greatest hitters in baseball history and to date is the last player to hit over .400 in a season. His .482 on-base percentage is the highest of all time.