Jamie Moyer (born November 18, 1962) is an American former professional baseball pitcher. Over his 25-year career in Major League Baseball (MLB), Moyer pitched for the Chicago Cubs, Texas Rangers, St. Louis Cardinals, Baltimore Orioles, Boston Red Sox, Seattle Mariners, Philadelphia Phillies, and Colorado Rockies.

At the time of his final game, he was the oldest player in the major leagues and had the most wins, losses, and strikeouts of any active MLB pitcher. He was likened to Phil Niekro due to his long career and relatively old age upon retirement. On April 17, 2012, Moyer became the oldest pitcher in MLB history to win a game. On May 16, 2012, he broke his own winning-pitcher record and also set the record for the oldest MLB player to record a run batted in (RBI). He also holds the major league record for most home runs allowed with 522.

Moyer made the All-Star team in 2003, while with the Mariners. Moyer has received numerous awards for philanthropy and community service, including the 2003 Roberto Clemente Award, the 2003 Lou Gehrig Memorial Award, the 2003 Hutch Award, and the 2004 Branch Rickey Award. Moyer is one of 31 players in baseball history to date to have appeared in MLB games in four decades. At the time of his retirement, Moyer had faced 8.9% of all MLB hitters ever. He was inducted into the Mariners Hall of Fame in 2015.

Moyer attended Souderton Area High School in Souderton, Pennsylvania, where he played baseball, basketball, and golf. In his junior year of baseball, he had a 10–0 win–loss record and threw three consecutive no-hitters.

Moyer enrolled at Saint Joseph's University and played college baseball for the Saint Joseph's Hawks baseball team. In 1984, he set the school's single-season records in wins, with 16, earned run average (ERA), with 1.99, and strikeouts, with 90. In 1997, he was one of three inductees into the first class of the Saint Joseph's Baseball Hall of Fame. In 2018, he became the only Saint Joseph's baseball player to have his jersey number, number 10, retired.

The Chicago Cubs selected Moyer in the sixth round of the 1984 amateur draft. Moyer was selected a New York–Penn League All-Star in 1984. He made his major league debut with the Cubs on June 16, 1986, against Steve Carlton and the Philadelphia Phillies, and earned his first win. On August 16, he threw his first shutout against the Montreal Expos. He was also the starting pitcher for the Cubs on the day that Greg Maddux made his major league debut.

In 1987, Moyer ranked tenth in the National League in strikeouts with 147, while winning 12 games and losing 15. He also lost 15 games in 1988 against only nine wins. Despite his poor record, Moyer lowered his ERA to 3.48 (it had been 5.10 in 1987), and while he struck out fewer batters than he had in the previous year, he decreased his walk rate significantly, giving only 55 batters a base on balls as opposed to 97 in the previous year.

Following his then-best season in 1988, the Cubs traded Moyer, Rafael Palmeiro, and Drew Hall to the Texas Rangers for Mitch Williams, Paul Kilgus, Curtis Wilkerson, Steve Wilson, Luis Benitez, and Pablo Delgado.