Financial terms were not released by the Angels, but sources told ESPN.com the deal with the two-time All-Star is worth $144.5 million.
The Angels announced the deal with the 22-year-old, saying Trout and his family will be at a news conference Saturday in Anaheim to formally announce the contract along with owner Arte Moreno, manager Mike Scioscia and general manager Jerry Dipoto.
Few players in major league history have approached Trout's accomplishments in his first two full major league seasons. The speedy outfielder is a five-tool player and one of the darlings of baseball's sabermetrics crowd, known for putting up old-fashioned highlights and statistical superlatives on a regular basis.
The Millville, N.J., product was a unanimous choice for AL Rookie of the Year in 2012, and he finished second in AL MVP voting to Miguel Cabrera the past two years.
Trout's deal came on the same day Cabrera finalized a $292 million, 10-year deal with the Detroit Tigers, the richest contract in American sports.
The free-spending Angels were determined to reward Trout while locking up their prized possession beyond his first few years of eligibility for arbitration and free agency. Los Angeles has been quietly negotiating with Trout's representatives throughout spring training, and the club closed the deal three days before Opening Day at Angel Stadium.
Trout agreed on Feb. 26 to a $1 million, one-year contract for 2014, much more than the Angels were required to offer him. His new deal runs from 2015-20.
The outfielder would have been eligible for arbitration for the first time after this season, and for free agency following the 2017 World Series. Now, he can't become a free agent until at least age 29.
It's the latest big-money deal for the Angels, who are entering the third season of a $240 million, 10-year contract with first baseman Albert Pujols, the second season of a $125 million, five-year agreement with outfielder Josh Hamilton and the third season of an $85 million, five-year contract with pitcher Jered Weaver.
But while the Angels' deals for Pujols and Hamilton have been criticized for their lavish nature and the 30-something sluggers' ensuing lack of production, Los Angeles is locking up Trout early in an uncommonly promising career.
Trout's contract isn't worth as much as Cabrera's deal in Detroit, but it still would allow Trout to hit free agency at an age when he could be in the prime of his career.
And when his new deal ends, Trout will still be younger than the 30-year-old Cabrera is now.
Trout's average salary of $24,083,333 under the new deal is ninth in the majors, trailing only those of Clayton Kershaw, Cabrera, Alex Rodriguez, Justin Verlander, Ryan Howard, Hamilton, Felix Hernandez and Zack Greinke.
Trout is batting .314 with 62 homers and 196 RBIs in just 336 career games, including 40 games in 2011. He also has stolen 86 bases while playing stellar defense and making two All-Star teams, starting for the AL last summer.
He is one of four players in baseball history to bat .320 with 50 homers and 200 runs in his first two full seasons, joining Joe DiMaggio, Ted Williams and Pujols.
Trout has accomplished just about everything except team success during his short major league career. The Angels have missed the playoffs in four consecutive seasons, and they finished 78-84 last year, their worst record in a decade.
The deal provides huge security for Trout. He received a bonus of $1,215,000 when he signed after the Angels selected him with the 25th overall pick in the 2009 amateur draft. He made $482,500 two years ago and earned a $10,000 bonus for winning the rookie award, then was unilaterally renewed by the Angels last year at $510,000 -- $20,000 above the big league minimum at the time.
That deal sparked criticism from many Angels fans who thought Trout deserved more compensation for his outstanding play. They also worried the relatively meager deal -- and the Angels' decision to move Trout from his preferred center field to left last season -- might sour the budding superstar on the team.
Trout is back in center field this season, and Moreno made sure Trout couldn't doubt the Angels' financial commitment to him.
ESPN.com's Jerry Crasnick, ESPNLosAngeles.com's Mark Saxon and The Associated Press contributed to this report.