The Warriors inflicted the first 4-0 NBA Finals blanking since the Cavaliers were swept by San Antonio in 2007.
"This is so hard to do and to do it three years out of four years is incredible," Warriors guard Klay Thompson said.
Stephen Curry scored 37 points and Kevin Durant, the NBA Finals Most Valuable Player for the second year in a row, added 20 points, 12 rebounds and 10 assists for the first finals triple double of his career.
"It's an unbelievable feeling to come here with a mission and get the job done," Curry said. "They made some mini-runs, but over the course of 48 minutes our will took over."
Golden State claimed the sixth crown in club history, matching the Chicago Bulls for third on the all-time list. The Warriors also won in 1947 and 1956 when based in Philadelphia plus 1975, 2015 and 2017 after their move to the San Francisco Bay area in 1962.
"This was the hardest one we've had by far," Warriors coach Steve Kerr said.
It was the fourth year in a row the Warriors met Cleveland in the finals.
"We used the experience last year to our advantage," Curry said. "We knew they were going to come out with a tough first punch and we answered it and ran right back at them, set the tone for the whole game."
Cavaliers star LeBron James, playing in his eighth consecutive finals, scored 23 points, grabbed seven rebounds and passed off eight assists but fell to 3-6 in the championship series for his career, having twice won with Miami and triumphed again with Cleveland in 2016.
James might have played his final game for the Cavaliers. He can opt out of his contract and become a free agent next month.
"I hope he stays," Cavs coach Tyronn Lue said.
Fans chanted "M-V-P" to James in the final minutes, sensing his possible exit again. He departed in 2010 for Miami before returning in 2014.
"Sometimes you can give everything you've got and still come up short and that's what happened to us," Lue said.
Curry, who set an NBA Finals record with nine 3-pointers in game two, hit 12-of-27 shots from the field and 7-of-15 from 3-point range.
"We just know how to win," Curry said. "We keep waking up every day and trying to get better and we end up here. For us to be able to be here again, we can't get enough of this feeling."
- 'About the journey' -
Durant, who had a playoff career-best 43 points in game three, became only the sixth back-to-back finals MVP.
"This is about the journey. All season, getting up, going to work with these guys is amazing," Durant said.
"It's good for you to be around guys like this, it makes you a better basketball player and a better man.
"It's a journey that's better than the destination. I'm happy to be part of this group."
An 11-2 Warriors run put Golden State ahead 24-13 on the way to a 34-25 lead after the first quarter.
A James slam dunk capped a 14-4 Cavs run to open the second quarter, putting Cleveland ahead 39-38, but Golden State answered with a 11-4 run and stretched the half-time lead to 61-52.
Curry scored 20 points in the first half, hitting 4-of-6 3-point shots, as Golden State seized a 61-52 half-time edge.
The Cavaliers would come no closer in the second half.
Golden State outscored Cleveland 25-13 in the third quarter, James managing only four points -- all on free throws -- in the period, and the Warriors rolled through the final minutes to another coronation.
James was removed with 4:03 remaining and congratulated the Warriors before taking a seat on the bench.
"When you play one of the best it brings the best out of you as well," Durant said of playing against James.
James, 33, is the oldest finals leader in points and minutes, having struck for 51 points in the opener, the fifth-best game total in finals history.