The Golden State Warriors earned their third NBA title in four seasons after completing a comprehensive 4-0 series win over the Cleveland Cavaliers.

Coach Steve Kerr described the triumph as "the hardest so far" but his Warriors side routed the Cavs 108-84 to prevail in the fourth consecutive finals meeting between the teams.

Stephen Curry scored 37 points for the Warriors, while LeBron James claimed 23 in what could be his final Cavs game.

James is a free agent next month.

The 33-year-old American, playing in his eighth consecutive finals, said he had "no idea at this point" about his future and would consider the decision with his family.

'We just know how to win'

The win added to the Golden State Warriors' victories in 2015 and 2017 and was the first finals clean sweep since the Cavs were demolished by San Antonio Spurs in 2007.

It was the second time the Warriors have secured the championship in Cleveland during Kerr's four-year tenure.

"I remember sitting in this room three years ago and it seemed like a dream. This feels like reality," Kerr said. "I hope that doesn't sound arrogant. It's just the talent we have and the experience we've gained."

A James slam dunk had Cleveland ahead 39-38 halfway through the second quarter, but Golden State responded to lead 61-52 at half-time and eased to victory from there.

"We just know how to win," said Curry. "We keep waking up every day and trying to get better and we end up here. We can't get enough of this feeling.

"Wherever that puts us in the conversation in the history of the NBA or being a dynasty... we'll have plenty of time to discuss that later. We want to keep this thing going as long as we can."

Curry top scored but it was Kevin Durant who was named Finals MVP for the second year in a row, adding 20 points, 12 rebounds and a post-season career high of 10 assists.

It was the 28th consecutive play-off game in which he has scored at least 20 points.

"They have five guys on the floor that can dribble, pass and shoot," said Cavs coach Tyronn Lue. "Even when you do defend them well, they've got guys like Steph and KD who can make unbelievable shots."

'Broken hand was self-inflicted' - LeBron

While Golden State are building one of the great basketball dynasties, Cleveland's future is clouded by uncertainty.

James, widely regarded as the greatest player of his generation, is expected to leave for a second time, having returned to the franchise in 2014 after departing for Miami four years earlier.

The three-time champion revealed he had played the last three matches with a broken right hand, sustained after he scored his best play-off points haul of 51 in the opener.

The Cavs' talisman reportedly suffered the injury after punching a blackboard in frustration after his side spurned an opportunity to win in the final seconds.

"It was self-inflicted," he said. "I was very emotional for a lot of different reasons and I let that get the best of me."

On the night, James top scored for his side and left to a standing ovation after playing 41 of the game's first 44 minutes, but it was his least productive performance of the series.

"To be the best player in the world and to give everything you've got in your 15th season, play all 82 games and carry this team the way he did is a testament to his character," Lue said.

"He's a bad boy and I love having him on our team. He fights and competes to the end. Sometimes you can give everything you've got and still come up short.

"I hope he stays. But after a game like that I'm not in any position to talk about that."