Jalen Brunson sparked one of the NBA’s greatest postseason comebacks, a rally from a 22-point deficit in the fourth quarter, and finished with 38 points as New York beat the Cleveland Cavaliers 115-104 in overtime in Game 1 of the Eastern Conference finals.

After a record-setting run through the first two rounds, the Knicks were going nowhere for 40 minutes against the Cavs, trailing 93-71 with 7:52 to play. But Brunson relentlessly attacked James Harden to spark an 18-1 run, and he tied the game at 101-101 on a basket with 19 seconds remaining in regulation.

The Knicks then opened overtime with a 9-0 run as a delirious crowd at Madison Square Garden danced and screamed in the aisles. The Knicks moved within three wins of their first NBA finals appearance since 1999.

“I don’t have an answer for you,” Brunson told ESPN when asked how the Knicks staged their comeback. “We got some stops, we kept fighting, kept believing. Just kept chipping away. They were playing great basketball, and we just found a way.”

Mikal Bridges added 18 points and three Knicks scored 13, including OG Anunoby, who came on late after struggling most of the way in his return after missing two games through injury.

Donovan Mitchell scored 29 points for the Cavaliers, who seemed well on their way to a third straight road win before their late collapse.

“We played great basketball tonight for three quarters. Unfortunately, the fourth quarter – they dominated us in the fourth quarter,” Cavs coach Kenny Atkinson said.

The Knicks had outscored Atlanta and Philadelphia by a combined 194 points, the largest margin ever through a team’s first 10 postseason games. But after not playing since 10 May, when they finished their second-round sweep of the 76ers, the Knicks misfired most of the night, looking like the rust hurt more than the rest helped.

They were 4 for 23 on three-pointers through three quarters and then had a horrible start the fourth. But a year after coughing up a 14-point lead in the final minutes of regulation and losing to Indiana in OT in Game 1 of the conference finals on their home court, the Knicks found their offense just in time.

The only larger fourth-quarter playoff comeback in the last 30 years was when the Clippers rallied from 24 down to beat Memphis in Game 1 in 2012.

The Knicks came from 20 points behind three times last year in the postseason. Those were their largest comebacks on record since 1969-70, when they won their first of two NBA titles.

The Knicks have won eight straight games and will host Game 2 on Thursday.