The 36-year-old former England captain signed the two-year deal with the Major League Soccer club after turning down a chance to move back to Europe with Paris Saint-Germain.
"This was an important decision for me," Beckham said in a statement provided to The Associated Press. "I had many offers from clubs from around the world, however, I'm still passionate about playing in America and winning trophies with the Galaxy."
His agreement was first reported by the Los Angeles Times.
The midfielder joined the Galaxy in 2007 from Real Madrid with a US$32.5 million, five-year contract. But he didn't lift his first trophy in the U.S. until the Galaxy won the MLS Cup in November.
Beckham, who started his career at Manchester United, opted against moving to France or returning to the Premier League because his family is settled in California.
He is targeting a spot in Britain's Olympic soccer team at the London Games by playing regularly for the Galaxy.
"I've seen first hand how popular soccer is now in the States and I'm as committed as ever to growing the game here," Beckham said. "My family and I are incredibly happy and settled in America and we look forward to spending many more years here."
The Galaxy, though, knows how close they came to losing the player who gives the team international fame.
"I am thrilled that David has chosen to rejoin the Galaxy, especially as he had numerous options where he could continue his career," Galaxy coach Bruce Arena said. "I felt that he was one of the best players in all of MLS last season and we could not have achieved the success that we did without him. We look forward to trying to replicate that success this season with David once again in a Galaxy uniform."
It is a jersey that the Galaxy said is the bestselling in the MLS and "one of the best in the world."
"There has been much speculation in the past four months on where David was going to play and we did not get caught up in this and remained focused on re-signing him," said Tim Leiweke, president of team owner AEG. "David had many options and we are pleased he felt comfortable, not only with our organization but also with Los Angeles, and will remain an important part of our club, our AEG family and our City."
Beckham's deal was negotiated by Simon Fuller, the creator of reality TV hit "American Idol," who is the player's business partner and manager.
"When David and I discussed making the move from Real Madrid to the LA Galaxy back in 2007, our minds were firmly focused on the massive opportunity of helping to grow soccer in the United States," Fuller said. "We have made great progress over the past five years in raising the profile of soccer domestically and the MLS on a worldwide stage, and we are encouraged by all the results.
"However, clearly this is an ongoing mission and this new deal confirms our commitment to continuing our journey and making sure the world's biggest sport, soccer, continues to grow in the world's most passionate sports loving nation, the USA."