An infant is fighting for his life after falling today from the window of a Bronx apartment building, authorities said.

The two-year-old boy plummeted from the fourth-floor window of a six-story complex on Grand Avenue, near West Tremont Avenue, at about 7 p.m., fire officials said.

The child was rushed to St. Barnabas Hospital.

There are bars on the lower halves of the apartment’s windows.