A young mother was arrested Tuesday in the death of her 8-month-old little girl in their Bronx apartment, cops said.

Emily Ramirez, 23, was charged with criminally negligent homicide and acting in a manner injurious to a child after she left her tot in a bathtub with the water running while she left the room to do housework, according to the NYPD.

When Ramirez returned to the bathroom around 6:30 p.m. on July 3, Amelia Belle Perez was face down in the water, sources previously told The Post.

EMS responded to the third-floor apartment in the Murphy Houses on Vyse Avenue near East 173rd Street in Crotona Park and rushed the tot the hospital, where she was critical, cops said.

Amelia Belle Perez died almost two weeks later at Montefiore Children’s Hospital.