A Bronx man has been sentenced to 18 years in prison after pleading guilty to manslaughter in connection with the beating and stomping death of an 18-year-old Levittown man in 2011, Queens prosecutors said Wednesday.

Island Trees High School graduate Anthony Collao was leaving a Woodhaven birthday party he had attended with his girlfriend when he was chased through the street and attacked by a group of teens, prosecutors said.

Collao died two days later as a result of his injuries.

Alex Velez, 21, was one of six men accused in the attack. He pleaded guilty April 20. Three other people already have been sentenced for their role in the crime, according to prosecutors.

“The sentence imposed is a measure of justice for a brutal and unprovoked attack on a young man that cost him his life,” Queens District Attorney Richard A. Brown said in a statement.

According to prosecutors, Collao had just left a party on March 12, 2011, when Velez and five other men chased him down.

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The men had previously crashed the party and made derogatory remarks. Three of them were carrying what appeared to be a stick, a pipe and a cane, authorities said.

Just before 1 a.m., the group caught up with Collao on 90th Street and threw him to the ground. Prosecutors said they had “perceived him to be gay.” They punched, kicked and hit the victim before stealing his Atlanta Braves baseball cap and sneakers, authorities said.

Just 15 minutes after the assault, police picked up five of the defendants near Woodhaven Boulevard and Jamaica Avenue.

Police also recovered a metal pipe with blood on it near the victim and a piece of fencing used in the attack.

A sixth defendant was arrested three months later.

In addition to his prison term, Velez was sentenced Tuesday by state Supreme Court Justice Joseph Zayas in Queens to 5 years of post-release supervision.

His attorney, David Bart, could not be reached.