LeBron James powered the Cleveland Cavaliers to a 93-89 victory over the Golden State Warriors on Sunday in an electrifying Game Seven to complete an improbable comeback unlike any seen before and capture their first NBA championship.

With the win over the top-seeded Warriors, who celebrated a championship on Cleveland's home court last year, 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 the 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."

When the final buzzer sounded to end what was the closest game of the Finals, an emotional James dropped to the floor before he was mobbed by his teammates.

James led Cleveland in the championship-clinching win with a triple-double as he recorded 27 points, 11 rebounds and 11 assists en route to being named the Most Valuable Player of the NBA Finals for a third time.

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 came back for a reason. I came back to bring a championship to our city," said James, who was in tears as he wrapped his arms around the Larry O'Brien Championship Trophy.

"I knew what I was capable of doing. I knew what I learned in the last couple years that I was gone, and I knew I had the right ingredients and the right blueprint to help this franchise get back to a place that we've never been."

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.

"It wasn't easy what we accomplished, and it's not an easy pill to swallow what we didn't accomplish," said two-time league MVP Stephen Curry, who had 17 points in the loss. "So got to just take the good with the bad."

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.

The Warriors were ultimately undone in the series 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.

"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."

When the Warriors raced out to a 3-1 series lead the Cavs were left for dead by many impartial observers who expected the Golden State to run away with the series.

But with their backs against the wall, a Cavaliers team that once seem overmatched never gave up in their quest for a maiden NBA title.

"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."

Cleveland Cavaliers forward LeBron James (23) speaks to media with his children Lebron James Jr. and Zhuri James present following the 93-89 victory against the Golden State Warriors in game seven of the NBA Finals at Oracle Arena. Photo: Reuters