Fernando Valenzuela Anguamea (Latin American Spanish pronunciation: [feɾˈnando βalenˈswela]; born November 1, 1960) is a Mexican former professional baseball pitcher. Valenzuela played 17 Major League Baseball (MLB) seasons, from 1980 to 1991 and 1993 to 1997. While he played for six MLB teams, his longest tenure was with the Los Angeles Dodgers. Valenzuela batted and threw left-handed. His career highlights include a win-loss record of 173–153, with an earned run average (ERA) of 3.54. His 41.5 career wins above replacement (according to Baseball-Reference) is the highest of any Mexican-born MLB player. Valenzuela had an unorthodox windup and was one of a small number of pitchers who threw a screwball regularly. Never a particularly hard thrower, the Dodgers felt he needed another pitch; he was taught the screwball in 1979 by teammate Bobby Castillo.

Valenzuela was signed by the Dodgers on July 6, 1979, and made his debut late in the 1980 season. In 1981, in what came to be called "Fernandomania", Valenzuela rose from relative obscurity to achieve stardom. He won his first eight starts (five of them shutouts). Valenzuela finished with a record of 13–7 and had a 2.48 ERA; the season was shortened by a player's strike. He became the first, and only, player to win both Cy Young and Rookie of the Year awards in the same season.

Valenzuela had the best period of his career from 1981 to 1986. He was named a National League (NL) All-Star in each season and won a National League-leading 21 games in 1986, although Mike Scott of the Houston Astros narrowly beat him out in the Cy Young Award voting. Valenzuela was also one of the better hitting pitchers of his era. He had ten career home runs and was occasionally used by Los Angeles Dodgers manager Tommy Lasorda as a pinch-hitter. However, for the remainder of Valenzuela's Dodgers career, his pitching efforts were rendered less effective, largely due to nagging shoulder problems. He was on the Dodgers’ 1988 World Series championship team, but he did not play that postseason because of his ailing shoulder. On June 29, 1990, Valenzuela threw his only MLB no-hitter, pitching at Dodger Stadium against the St. Louis Cardinals, a 6–0 victory. Despite having recently shown flashes of his former self, he was unceremoniously released by the Dodgers just prior to the 1991 season. The remainder of his big league career was spent with the California Angels, Baltimore Orioles, Philadelphia Phillies, San Diego Padres, and St. Louis Cardinals.

Valenzuela retired from baseball after the 1997 season. In 2003, he returned to the Dodgers as a broadcaster. In 2015, he became a naturalized American citizen.