James has played in eight straight NBA Finals from the Eastern Conference, with the Miami Heat and then with the Cavaliers.
"Thank you Northeast Ohio for an incredible four seasons", James wrote on his Instagram story.
The Lakers were considered one of the favorites to land James this offseason.
For the second time in his 15-year career, James will part with his home state team.
The other main team affected is the San Antonio Spurs, who are looking to deal unhappy star Kawhi Leonard to the Lakers.
The two-time Defensive Player of the Year had been cleared to return by the Spurs' medical staff but he didn't believe he was 100 percent healthy and sought a second opinion. The Philadelphia 76ers, a young team very much on the rise and has the money to spend, is out and about to try and get some big names this summer.
James was on a plane that flew into Van Nuys Airport in Los Angeles on Saturday, a source told ESPN.
The Lakers also didn't panic as it came time for LeBron to make his decision. Everyone was puzzled as to why the Nets would have made such a ridiculous move, but Pelinka and Johnson somehow convinced them to do so.
James has also endured a fractious relationship with Cavaliers fans over the years.More news: Canada to aid steel, aluminum industries hit by US tariffs
If James would have signed with Philly he would have helped improve an already stingy Sixers defense, which finished 11th in OPG.
LeBron James is leaving home for Hollywood and an iconic team. Teams can begin negotiations with free agents at 12:01 a.m. Sunday.
In terms of basketball reasons, James is still as hungry for ever for championships and after delivering his promise of bringing one to his hometown Cavaliers in 2016, he will feel he's entitled to move on.
James wasn't expected to drag his choice out over several days.
Irving has spent just one season with the 17-time National Basketball Association champions and despite his season being cut short by injury, he played a key role in helping them finish as the second seeds in the Eastern Conference.
A person with knowledge of the situation says the Dallas Mavericks are making another run at DeAndre Jordan, three years after the center jilted them in free agency to stay with the Los Angeles Clippers. Others competing for his signature can only offer a four-year contract worth $152 million.
The chance to play for one of America's most storied franchises is a new challenge for James, who prides himself on knowing the game's history.