A funky Upper West Sider is causing a disco ball inferno on West 86th Street.

Residents are not digging the blinding purple light caused by what they assumed was a disco ball on the ninth floor of the Dexter House hostel between West End Avenue and Riverside Drive.

One even raged that “Disco guy” was causing “light pollution.”

“At night, the light flashes in the windows of all the apartments across the street all night and is extremely disruptive,” one anonymous tipster told West Side Rag.

“We have tried contacting the non-emergency police number, and they said there’s nothing they can do about it because no law is being broken.”

“Disco guy” simply isn’t being groovy to his neighbors, locals said.

“Should we also defend the person upstairs that tap dances from 3am – 5am?” another person asked in the publication.

“I think the disco ball owner is not being a good neighbor,” another said.

Others said disco should stay dead — because the light may be hazardous to their health.

“Neighbors are being hurt by light pollution,” one declared.

“Light pollution is a serious problem and flashing lights can cause seizures,” someone else added on the site.

The ninth floor resident revealed to The Post Saturday the glow was not from a disco ball but from a powerful, pulsating and rotating $2.50 Christmas light — insisting he had no clue it was getting his neighbors’ tinsel in a tangle. 

“I would never think this would create such a scandal,” said the man, who only spoke Spanish and declined to give his name. The doorman at the building told The Post he never received any complaints.

“People have the right to think what they want. I didn’t want any problems,” the resident said.

The resident, who moved in about six months ago, said he purchased the illuminating orb three weeks ago at a 99 cent store “to feel happy in my room for the holiday.”

“What problem is this creating? I stay in my room, I am peaceful, I am not bad,” he added.

Upon hearing about the uproar, he took his light down, and handed it over to his friend and neighbor, Carol Moody.

“Look how respectable he is, you told him there is a problem and he took it down. They should have come here and told the doorman, and the doorman would talk to him. This is crazy,” she said.

A majority of commenters agreed — saying they thought the man’s apartment vibes were far out.

“I don’t suppose any of the claimants have ever heard of shades, drapes or blinds,” one quipped.

“Let’s hear it for UWS privilege,” another added.

“All these liberals with their artisanal lattes and their over the counter omakases, Jean-George French laundry turn down service — can’t even deal with a little Disco Fever,” one said.

“A little disco never hurt anybody,” another added.