A man was seriously injured Monday morning when he was stabbed by a stranger in front of a Greenwich Village diner, authorities said.

The victim, who is about 45 years old, was stabbed in the back around 4:45 a.m. in front of the Waverly Diner at the corner of Waverly Place and Sixth Avenue, police said.

He was rushed to Bellevue Hospital in serious condition with a non-life-threatening wound, an FDNY spokeswoman said.

It wasn’t immediately clear where the victim is from or what, if anything, prompted the assault.

Police were not immediately able to provide a description of the attacker, who is still on the loose.