A courageous teller laughed in the face of a would-be bandit who demanded cash from her in a lower Manhattan bank, police said yesterday.

The 25-year-old teller was working at the Citibank branch at 127 Hudson St. at around 5 p.m. Monday, when the unidentified man strolled up and stated, “Excuse me, miss. This is a robbery. Give me all your large bills. Don’t do anything stupid.”

The teller thought it was a joke and started laughing. The perp repeated, “Give me all your large bills” — but she still refused.

The crook fled, empty-handed.