A 48-year-old man was fatally stabbed by his girlfriend inside an Upper West Side apartment on Monday night, police sources said.

Cops said they found the man at about 9 p.m. with multiple stab wounds to his chest inside a second-floor apartment on Amsterdam Avenue near West 91st Street.

He was taken to St. Luke’s Hospital and pronounced dead.

Tracy McCarter, the victim’s 44-year-old girlfriend, was arrested and charged with murder and criminal possession of a weapon.