Troy Eugene Percival (born August 9, 1969) is an American professional baseball coach and former pitcher. He is currently the manager of the Long Beach Coast of the Pioneer League. During a 14-year baseball career spanning from 1995 to 2009, he pitched for four Major League Baseball (MLB) teams, primarily with the California/Anaheim Angels. He was an integral part of that franchise's 2002 World Series championship team, and gained fame as a closer.

Percival started playing baseball at Moreno Valley Youth Federation (MVYF). Percival played on the Moreno Valley High School baseball team, before attending the University of California, Riverside, where he played college baseball for the Highlanders from 1987–1990.

Percival was then drafted by the California Angels in the 6th round, with the 175th overall selection, of the 1990 Major League Baseball draft as a catcher. He batted .203 in his only season as a catcher with the Boise Hawks and was converted to a pitcher when coaches noticed that his return throws to the mound were actually faster than the pitches he caught. He made his major league debut as a reliever in 1995, and was mostly used as a setup man for Lee Smith. He was coached by his father Richard Percival for all of his childhood years.

In 1996, he became the regular closer for the Angels and had 36 saves with 100 strikeouts in 74 innings. He is one of only six pitchers in the Angels' 44-year history to strike out at least 100 batters in a season without starting a game. The others are Mark Clear (105, 1980), DeWayne Buice (109, 1987), Bryan Harvey (101, 1991) Scot Shields (109, 2004) and Francisco Rodríguez (123, 2004).

He had a career-high 42 saves in 1998, and enjoyed his best season in 2002 with a 4–1 record, 40 saves, 68 strikeouts, and a 1.92 ERA. That year en route to winning the World Series, he was 7 for 7 in save opportunities, tying John Wetteland for most saves in one postseason (since tied by Brad Lidge, Koji Uehara and Greg Holland; Robb Nen was also 7 for 7 but blew one on the eighth opportunity).

A four-time All-Star, Percival compiled a 29–38 record with a 2.99 ERA in 586.2 innings for the Angels. His 355 saves grant him inclusion in the 300 save club. However, his strikeouts per nine innings went down considerably after his years as an elite closer. In 2001, his K/9 rate was 11.08 and decreased to 5.98 in 2004. His fastball, once clocked consistently at 96–100 MPH, was down to about 92–93 MPH in 2004, due to a degenerative hip condition that first appeared in 2003, which forced him to alter his pitching delivery.

Percival's contract with the Angels expired in 2004 and he became a free agent at the end of that season. Rather than bring Percival back, the Angels decided to turn to young phenom Francisco Rodríguez to close, motivated largely by Rodríguez's much lower price tag and concerns about Percival's age and health. The Angels offered to negotiate a reduced role (at a correspondingly reduced salary) for Percival to return as a setup man, but Percival decided to seek opportunities elsewhere that would allow him to remain a closer.

Percival signed with the Detroit Tigers as a free agent for the 2005 season. However, after a mediocre start to his career at Comerica Park, during which he converted eight saves from 11 opportunities and posted an ERA of 5.76, Percival suffered a serious injury to his right forearm in early July. The severity of the injury ended his season, and put the rest of his career in doubt.