"I’m very excited to begin the next chapter of my career in the United States with LA Galaxy,” Gerrard told the MLS club's official website (www.lagalaxy.com).
"The Galaxy are the most successful club in Major League Soccer history and I am looking forward to competing for more championships in the years to come," he added.
Gerrard told the Liverpool Echo on Tuesday he would have agreed to continue his long Liverpool career had the club offered him a new contract.
Instead, the 34-year-old will now join a growing list of high-profile former Premier League players to cross the Atlantic in the latter stages of their careers, most notably David Beckham.
Former Tottenham Hotspur and Liverpool striker Robbie Keane will be a team mate of Gerrard at the Galaxy while former Chelsea midfielder Frank Lampard has signed for New York City FC, although he is still in England on loan at Manchester City.
"I am committed to helping the LA Galaxy compete for trophies and to having an impact in Los Angeles and I will give my all for the club. In the meantime, I will continue to give everything for Liverpool for the remainder of this season before joining up with the Galaxy," said Gerrard.
Former England captain Gerrard has spent his entire career at Liverpool, making nearly 700 appearances and winning the Champions League, FA Cup and League Cup.
"We’re very pleased to acquire a player of Steven’s calibre, experience and character,” LA Galaxy head coach and general manager Bruce Arena said.
"He is one of the most decorated players in the world and will join our team with a wealth of success playing at the highest level of the sport. Steven will be an excellent example to our young players and we’re excited to add him and his leadership to an already talented roster," said the former US national team coach.
Image: Steven Gerrard
Photograph: Phil Noble/Reuters
Gerrard confirms he will head to MLS
Gerrard will join LA Galaxy, says it's a match made in heaven
Gerrard close to deal with LA Galaxy: ESPN
Lampard's decision to stay at City angers New York fans
Lampard to stay with Man City till end of season