NEW YORK — Mets slugger Pete Alonso has become the first rookie in 81 years to break his team’s season home run record.

Alonso launched his 42nd of the season on the first pitch from Chicago Cubs right-hander Yu Darvish in the fourth inning Tuesday night, a no-doubt drive to the opposite field that soared far beyond the fence in right.

He set the Mets mark with 31 games to spare.

Todd Hundley in 1996 and Carlos Beltran a decade later hit 41 homers for New York.