A creep followed and robbed a woman into her apartment building in Flatbush — and then masturbated on her, cops said Thursday.

The disgusting encounter happened just before 11:45 p.m. on Wednesday after the 25-year-old woman got off the subway near 5th Avenue and 45th Street, according to the NYPD.

The unknown creep tailed the woman from the subway, following her up the stairs at her apartment building and demanded her belongings, cops said.

“Let me get all your stuff,” the man said, acting as if he had a firearm and grabbed her cell phone and credit cards, according to police.

The creep then bent the woman over and masturbated on her before taking off, police said.

Cops are still hunting for the man, who is believed to be homeless, according to sources.