At least a dozen homeless people — each a “different shade of crazy” — have colonized the historic Manhattan Bridge colonnade, terrifying residents and littering the century-old neoclassical structure with shacks, tarps and tents.

Nearby businesses and residents told The Post that their new neighbors aren’t just a plague near the 111-year-old span once hailed as the gateway to the Big Apple — they’re also dangerous, throwing objects when jostled, stealing and even pooping al fresco.

“Every day is a problem,” said Zhong Yi Wang, 53, who runs his family’s restaurant, Jisu on Canal Street, where he said three bamboo plants – which cost $800 a pop – recently went missing .

Residents of the bridge often urinate on his door, knock on his window and even burst inside to yell at him, he said.

Urine isn’t the worst, according to a woman who works at the nearby Mahayana temple.

“Someone pooped in front of the temple,” said the woman, who only goes by her first name, Cindy. “And when we talk to them, they throw things at you and do all kinds of weird things.”

“It’s not so safe,” she continued outside the Buddhist place of worship. “They will try to hit you or kick you, you have to run away.”

Even other homeless people now avoid the neighborhood.

“It’s really sketchy out there, man. It’s not my scene. They’re junkies out there,” said a homeless man who said his name was Jonathan, 47.

Those who live on the colonnade have conceded to The Post that it is a dangerous drug den where people do anything to survive.

“Everyone here is a different shade of crazy,” said one resident, who went by the name Ray, 41. this.”

Ray decided to settle between two granite Tuscan columns on the north side of the bridge approach about three weeks ago when “the money ran out”, he said.

With a shovel he “got” from the city’s park department, he said, he cleans up trash, including needles. “A lot of people here use drugs,” he said.

When he needs money: “DoorDash. Or pretty much f-king steal. I’ll be honest, steal shit. […] It’s silly, like someone leaving a bike behind but not chaining it up properly.

Scattered around the square: garbage cans, searched suitcases, three Citi bicycles, a propane grill.

As Ray was speaking with The Post, one of his neighbors approached with a well-groomed German Shepherd tied to a chain.

“He stole a fucking dog!” Ray said. “Who did you steal the dog from, Nico?”

No answer.

South across the plaza – and roaring traffic lanes to Manhattan – city notices posted by another slum warn of a cleanup scheduled for Nov. 1.

Cleanups are periodic, Ray explained — but since the city gives advance notice, on the appointed day he will dismantle his shelter and decamp to nearby Sara D. Roosevelt Park.

The Beaux-Arts approach to the bridge, completed in 1915, was envisioned as an adornment to the City Beautiful era of a major metropolis.

At the time, bridge commissioner Arthur K. O’Keefe described the planned approach as “probably the most artistic treatment of a bridge entrance that has yet been attempted on this continent”, reported the predecessor of this newspaper, the “New York Evening Post”. April 17, 1913.

He compared it to the work of Bernini, the Renaissance sculptor and architect who designed the colonnade embracing St. Peter’s Square in Rome.