A Carnival Cruise ship passenger pleaded guilty to smashing his cocktail glass into a man’s face and beating him – after the victim asked him to quiet down during a theater show.

Michael Truman, 39, of Portsmouth, Virginia, was on the Carnival Magic liner off the coast of Nantucket, Massachusetts, on Oct. 20 when he sat on a barstool during the theater show of the production “Flick,” the feds said.

He was loud and appeared to be intoxicated so another passenger, identified as “J.H.” in court papers obtained by The Post, told him to quiet down.

Truman refused after being asked again so J.H. got up to find an employee to remove the alleged loudmouth, according to the criminal affidavit.

But as he tried to walk by, “Truman picked up his drink glass and smashed it into J.H.’s face. Truman then got on top of J.H. and began striking him,” the filing states.

The victim suffered facial cuts that required about 16 stitches, officials said.

When security personnel entered Truman’s cabin he “had removed his shirt and was holding a towel in his right hand, which was actively bleeding from a laceration,” according to the affidavit.

He claimed that he had been “clapping a lot” during the show and that a stranger asked him to stop doing so loudly.

Truman further claimed he hit J.H. only after the passenger had swung at him first.

“When asked ‘with what’ Truman hit the other person, Truman stated that he did not know,” the document says.

“Truman also stated that he did not know how he got the cut on his hand, claimed he had consumed three or four drinks of alcohol that day, and offered to stay in his room for the rest of the cruise,” it states.

He repeatedly claimed he had been defending himself.

“A broken old fashioned/lowball cocktail glass was found in the vicinity of the assault,” according to the filing.

On Feb.15, Truman pleaded guilty to assaulting the fellow passenger with a dangerous weapon, the US Attorney’s Office for the Eastern District of Virginia said in a release.

He is scheduled to be sentenced Aug. 29 and faces a maximum penalty of 10 years in prison.  

Carnival and Truman’s attorney Nicholas Ryan Hobbs did not return The Post’s requests for comment.