A convicted felon started a gasoline fire in a Brooklyn housing development in a scary attempt to torch the apartment where his ex-girlfriend and their daughter live, the feds allege.

Michael Rosendary lit the blaze in a 14th floor hallway outside his ex’s door in the Unity Towers on W. 27th St. in Coney Island, according to federal prosecutors.

The flames spread down the hallway as the target of his ire slept on her couch, but luckily, she awoke to see the glow under her door and had her daughter call 911, the feds say.

Rosendary, 47, was busted late last week on a federal arson charge for the May 17 blaze, which prosecutors said had the potential to cause a mass tragedy if it had burned out of control.

It wasn’t the first time Rosendary has tried to burn down a woman’s apartment, according to the feds. In 2006, he torched a woman’s apartment door after she refused to let him in, leading to an attempted arson arrest and a criminal contempt conviction, according to court filings.

Rosendary’s dangerous rage was kindled by a text message argument he had with the victim, who’s the mother of two of his children, according to federal prosecutors.

At about midnight, Rosendary headed over to a gas station on Cropsey Ave., about a six-minute drive from where the woman lived, and bought some gas — apparently pouring some of it into a water bottle, the feds allege.

He then drove back to the Coney Island Houses and walked into her building with the water bottle, the feds allege. At 12:16 p.m., two minutes before the daughter’s 911 call, security foodage shows him fleeing the building, the feds say. He no longer has the water bottle.

A joint NYPD-ATF Arson and Explosive Task Force started investigating the blaze tracked down the video of Rosendary buying gas, and showed it to the victim, who recognized him, the feds said.

In a letter to a federal judge, Assistant U.S. Attorney Molly Delaney called Rosendary’s alleged actions “profoundly dangerous.”

“The fire had already begun to spread from the victim’s door and could easily have continued to spread causing widespread destruction to both lives and property. The results could have been tragic,” she wrote, asking Brooklyn Federal Court Magistrate Judge Vera Scanlon to lock Rosendary up without bail.

The judge agreed, ordering his detention because of the “exceptional risk” to the alleged victim after a hearing Thursday.

Delaney also pointed out Rosendary’s 11 prior arrests and one prior felony conviction. He was free on bail in a state weapon possession case, after cops say he threatened people with a gun and fired into the air in Brooklyn in September, the prosecutor wrote.

He had a build-it-yourself ghost gun in the car with him when he was arrested, according to a criminal complaint.

Rosendary’s lawyer did not immediately return a message seeking comment Monday.