A 55-year-old man lost eight teeth in a vicious beat-down on a city bus in the Bronx, police said Sunday.

Authorities are still hunting the heartless thug who left the man in hospital after the senseless beatdown just after 11 p.m. on July 2.

According to cops, the unidentified man approached victim Dion Strickland while they were both riding on an MTA BX39 bus traveling on southbound and began slugging him repeatedly in the face.

The brute hopped off the bus on East 180th Street and Third Avenue in the Van Nest neighborhood and fled, according to cops.

Strickland suffered swelling and pain to his mouth and both eyes.

The victim took himself to a local hospital where he was treated for eight missing teeth.

Police say the attack was unprovoked and have asked for help identifying the attacker who was wearing a blue T-shirt emblazoned with the words “New York” and a silver chain.

It’s unclear what sparked the assault, but neighbors in Strickland’s apartment building on 181st Street in the Bronx told The Post that Strickland was a quiet man who kept to himself.

Neighbors said they hadn’t seen Strickland for a few weeks and didn’t even know he had been assaulted.

It’s believed he lives with his elderly mother.

The vicious beat-down comes just weeks after state officials announced they were assigning an extra 500 police officers to New York City’s transit system amid a jump in fare evasion and assaults on MTA employees.

Earlier this month, a Brooklyn man was arrested and charged for throwing urine in the face of a female bus driver and a female conductor on July 12.

Police finally caught up with Brandon Jobson 22, on July 4 and charged him with two counts of assault.

Victim Trellis Robinson was operating the BX2 bus in the Bronx when she was attacked and told PIX-11 the assaults were all too common.

“This is what us operators go through every day. All we’re doing is out there trying to move New York, feed our families, get people from point A to point B,” Robinson said.

Anyone with information about the July 2 beatdown is asked to call Crime Stoppers at (800) 577-TIPS.