A 34-year-old man was stabbed in the chest early Saturday in an unprovoked attack in Brooklyn, police said.

The victim was leaving a lounge to meet a friend around 5:16 a.m. at the corner of Avenue U and E. 23rd St. in Sheepshead Bay when the assailant came up to him and punched him in the face, then stabbed him in the right side of the chest, cops said.

EMS transported the victim to Coney Island Hospital in stable condition.

No arrests were made.

Cops are looking for a masked man wearing all black clothing who fled east on Avenue U.