With the victory over the top-seeded Warriors, who beat Cleveland in last year's championship, the Cavaliers became the first team to rally from a 3-1 series deficit in the best-of-seven NBA Finals and win the title.
"I've had goal for two years since I came back to bring a championship to the city," said an emotional James, who returned to the Cavaliers in 2014 after a four-year stint with Miami that included a pair of NBA championships.
"I gave it everything that I had. I poured my heart, my blood, my sweat and my tears into this game."
James led Cleveland in the championship-clinching with a triple-double as he scored 27 points to go along with 11 rebounds and 11 assists en route to being named the Most Valuable Player of the NBA Finals.
The win ends decades of heartbreak for the city of Cleveland, which had not won a professional sports championship since the 1964 Cleveland Browns of the National Football League.
For James, the win not only marks his third NBA title, but it will go down as the single greatest achievement of his storied career as it fulfills his promise to deliver a title to his home state of Ohio.
"I understand what everyone in northeastern Ohio have been through the last 50-plus years and I am happy to be a part of history," said James, who was in tears as he wrapped his arms around the Larry O'Brien Championship Trophy. "I can't wait to get back home. I am ready to get to you guys."
The back-and-forth game lived up to its billing as it was tight throughout and included 20 lead changes while no team was able to pull ahead by more than eight points.
Facing elimination in each of their previous two games, James carried the Cavs back from the brink as they became only the third team to force a Game Seven after falling behind 3-1 in the championship round.
For the Warriors, who had a record 73 wins during the 82-game regular season, Sunday's defeat marked the first time since November 2013 that they have lost three consecutive games.
The Warriors were in complete control of the series but were ultimately undone by the disappearance of their high-octane offense, a suspension to defensive stalwart Draymond Green, a season-ending injury to rim-protecting center Andrew Bogut and defensive specialist Andre Iguodala dealing with a balky back.
"I knew what we were capable of, even being down 3-1 versus the greatest regular season team ever," said James.
"Everybody counted us out and that's when we strived the most and that's definitely when I strived the most when everybody counted me out."
After a record smashing regular season the Warriors could not cap off the campaign with a second successive title, unable to deliver the knockout punch after going up 3-1 in the best-of-season series.
"Just an incredible run that obviously didn't end the way we wanted it to," said Warriors head coach Steve Kerr. "It's been an incredible two-year run. We're disappointed that it didn't go our way at the end, but that's life."