The city is so safe that the Guardian Angels had to start a side gig — as exterminators.

The vigilante group famous for taking subway safety into their own hands during New York’s bad old days are now targeting the Big Apple’s rat population, by using an army of feral cats.

Angels founder Curtis Sliwa’s girlfriend, Nancy Regula, has created colonies for the wild kitties that she traps and neuters — placing them in areas of rodent infestation.

She hopes to expand her program to all corners of the city.

“It’s a natural partnership,” Regula, who got the Guardian Angels involved with the program a few months ago, told The Post.

“They have an issue with rodents and as soon as they bring in a cat they’re gone.”

Regula and the Angels bring food and shelter to the colonies so the feisty felines will have a safe place to live while hunting down their prey.

Regula said putting them to work is a “sustainable” solution to all involved.

Bodega owners and property managers have long benefited from the free labor the feral cats offer.

“The cats don’t have a place to go, they can’t be adopted into a home,” Regula explained.

Courtney Chandel, who works with Regula, said some South Bronx residents have complained about the but it’s the lesser of two evils.

“You can either have cats or you can have rats so take your choice,” the colony manager said.

Daisy Alicea has been working with a colony near the Grand Concourse in the Bronx for eight years.

“They definitely serve a purpose — scouting the community and making sure it’s clean of rodents,” she said. “Grand concourse is a major roadway, it has a lot of rats and garbage…. you see rats running across the sidewalk.”

The block where her colony lives, right off the Grand Concourse, is rodent-free.

A few miles down the Grand Concourse, two people became severely ill from a rare bacterial disease linked to rats and another person died.

Jessica Guzman, 24, lives in one of the buildings the rat infection was linked to.

“I think they should keep cats,” Guzman said. “Cats would be good because they kill the rats. Someone needs to come get rid of them because there are so many.”