A Sag Harbor firefighter claims a fellow smoke-eater grabbed him by the crotch while the village’s mayor cheered him on — and that he was booted from the volunteer department when he complained, according to a lawsuit.

Noel Brandt was at a department event in June 2015 when an elderly member walked up, grabbed his crotch and held on, while then-Sag Harbor mayor Brian Gilbride — who is Brandt’s uncle — yelled encouragement, according to court papers.

Brandt later texted his disapproval to the bystanders, offering “a 2 for 1 sale on whoop ass,” he said in his Brooklyn federal court lawsuit against the village.

Instead of treating him as a victim of sexual assault, Fire Chief Thomas Gardella suspended Brandt and wouldn’t let him testify about what happened, Brandt charged. He was dropped from the fire department’s rolls last year.

Brandt is seeking more than $1.2 million. A village attorney did not return a message.