A 4-month-old baby girl has died after suffering head trauma inside her Brooklyn apartment — and her death has been ruled a homicide, police said Tuesday.

Cops responding to a 911 call found Madeline Makhnovsky with the injury inside her West 3rd Street home in Gravesend around 4 a.m. Dec. 12.

The infant was taken to Tisch Hospital in Manhattan and fought for her life for four days before dying.

No arrests have been made.