A fight in The Bronx that erupted over a woman turned deadly — with the woman’s new beau fatally stabbing her ex-boyfriend, cops said Monday.

The brawl between the two young men broke out around 6 a.m. Sunday in front of an apartment building on Simpson Street between Westchester Avenue and East 163rd Street, cops said.

Police said the two were warring over a woman who lived at the building.

Her 19-year-old ex was taken to NYC Health + Hospitals/Lincoln, where he died from multiple stab wounds to the torso, according to cops.

The woman’s current boyfriend, Dustin Dominicci, 18, was taken to the same hospital for a stab wound to the torso. He was listed in stable condition, police said.

Dominicci faces charges of murder, manslaughter and criminal possession of a weapon, cops said.