A piece of New York City history is bidding arrivederci.

Rising rents and changing demographics have driven Little Italy to the verge of extinction. Once a teeming neighborhood stretching 50 square blocks, it now barely covers three blocks of Mulberry Street — and even that strip is under threat.

“You can’t rebuild Little Italy,” said Robert Ianniello Jr., owner of the famed Umbertos Clam House. “If we go away, it will never be here again. You can’t build an Olive Garden and say it’s Little Italy.”

Ianniello is battling a rent increase from a new landlord who bought the building last month for $17.5 million. He recently got a rent bill for $34,000 a month — more than double what he used to pay.

“It’s a landlord problem,” said Ianniello, who heads the Little Italy Merchants Association. “They think this is Fifth Avenue.”

Eight eateries have shut down in the past year.

Il Fornaio, once owned by Gambino mobster Joseph Corrao, remains empty.

Giovanna’s shuttered after a six-year run when the landlord doubled the rent. Ads show the owner wants $32,000 monthly for the space.

A block south, at Positano Ristorante, a legal notice in the window shows the city marshal took over the storefront on behalf of the landlord in January.

At S.P.Q.R., the monthly rent jumped to more than $50,000 and the eatery was forced to close. The space currently is home to a year-round Christmas shop.

One Mulberry Street apartment building is converting the ground floor into retail, while a hotel is being constructed on Grand Street next to the now-shuttered Florio’s restaurant.

But it’s not just development that’s pressuring Little Italy. Cultural conflicts are also cutting it down to size.

In 2011, Nolita boutiques demanded the city remove three blocks from the famous Feast of San Gennaro to keep revelers’ “greasy hands” from besmirching their $300 frocks.

The shopkeepers’ request had festival boosters hotter than a plate of baked ziti. More than 100 protesters packed a community board meeting.

“We had Italians from all over writing to the mayor,” said John Fratta, whose grandfather co-founded the annual festival in 1926. “It’s something that’s very sacred . . . You’ll see venom if you try to change it or stop it.”

Italian immigration surged in the late 19th century. By the early 1900s, nearly 10,000 Italians lived in the neighborhood, which once spanned roughly from Lafayette Street to the Bowery and from Kenmare to Canal streets.

Many residents flocked to the outer boroughs after World War II, and an influx of Chinese immigrants moved in, blurring the lines between Chinatown and Little Italy.

Today Little Italy’s heart is three blocks of Mulberry Street between Canal and Broome streets.

Emelise Aleandri, an author on Italian history and theater, said that the neighborhood remains a cultural touchstone for Italian Americans across the country — and that it would be a huge loss if it disappeared.

“Right now, there is just enough of a population to keep up traditions,” Aleandri explained. “But it’s going to be more difficult to keep the area Italian if the merchants and businesses leave.”