The brute who sucker-punched “Boardwalk Empire” star Steve Buscemi in Manhattan last year mumbled a head-scratching apology Thursday — as he was sentenced to six months in jail.

Clifton Williams, 51, said he was “sorry” for assaulting Buscemi, 67, who was taking a stroll through Kips Bay when he walked up to the Hollywood icon and slugged him in the face on May 8, 2024.

“I only maintain the fact that there was an incident brought before me between myself and Mr. Buscemi on that date, and I’m sorry,” Williams said, wearing a tan prison jumpsuit as he faced Manhattan Supreme Court Judge Melissa Lewis.

Williams, who was homeless at the time, pleaded guilty to assault charges on March 12 and was also sentenced to five years probation and two orders of protection — one against Buscemi and another person he slugged the same day.

Prosecutors have said that Williams was walking on the sidewalk near East 15th Street and Third Avenue when he struck a 22-year-old man with a closed fist in an unprovoked attack at 11:30 a.m.

Nine minutes later, Williams then walked up to Buscemi and randomly clocked him in the face, causing Buscemi to fall to the ground, according to authorities. Williams then fled from the scene.

Williams was arrested more than a week after the attack after an eagle-eyed officer recognized him at a homeless services building in Chelsea, where the attacker was complaining about having property swiped.

Buscemi, known for roles in “Fargo” and “Billy Madison,” was spotted days later with a black eye and a swollen cheek while shooting a commercial in Soho.

Williams claimed that he mistook Buscemi for someone else he had known and that the actor had told him that he was going to “kick my ass” before the savage attack, court documents show.

Buscemi, who made a cameo appearance in Apple’s new show “The Studio,” was not in court for his attacker’s sentencing.

A publicist for Buscemi didn’t immediately respond to an inquiry from The Post.