Most stunning was establishing the NBA postseason mark for largest halftime lead, stretching it to 41 points with a JR Smith basket at the buzzer to take a 72-31 advantage.
The second-seeded Cavaliers' 44-point victory matched the fourth-largest road playoff margin in NBA history. The result also represented the widest margin of defeat for a No. 1 seed.
The Cavs scored the most points in a playoff game in franchise history and won by their largest postseason margin.
The Celtics' loss by 44 was the franchise's worst at home in the playoffs.
"It's honestly just embarrassing," Celtics guard Avery Bradley said.
"We got our ass kicked," Boston rookie Jaylen Brown said. "The defending champs swept us off the floor."
The Cavs won their 13th consecutive playoff game dating to last season, tying the Los Angeles Lakers from 1988 and 1989 for the all-time standard.
LeBron James had 30 points on 12 of 18 shooting, his ninth consecutive playoff game with at least 30 points. That ties the all-time playoff record held by Michael Jordan, who accomplished the feat twice. James also tied Kareem Abdul-Jabbar's mark of 10 straight games with 25 points and 50 percent or better shooting, set in 1970.
James has now personally won eight consecutive playoff games against the Celtics, dating to the 2012 playoffs with the Miami Heat. That is the second-longest streak for any player against Boston.
"I'm a guy who lives in the moment," James said, downplaying the performance. "Our team is in a great groove, and I'm happy to be a part of that groove."
James' teams have now been up 2-0 in playoff series 21 times, winning the previous 20.
The Cavs eventually pushed the Game 2 lead to as much as 50 points.
The final margin of 44 marked the second-worst playoff loss in Celtics history, after a 47-point defeat to the Orlando Magic in 1995.
"I just feel like we are in a great place where we're not looking for any excuses, not looking for anything to really motivate us other than for ourselves," said Cleveland point guard Kyrie Irving, who had 23 points on Friday. "We motivate each other."
Information from ESPN Stats & Information was used in this report.