The prison murder of James “Whitey” Bulger may have been done at the behest of another jailbird who claims the notorious Boston mob boss framed him for a slaying 38 years ago, according to a new report.

Former Mafia hitman Fotios “Freddy” Geas may have been seeking revenge on behalf of Frederick Weichel, a man he befriended during their stint behind bars in Shirley, Massachusetts, the Boston Globe reported.

Weichel told the newspaper that it was well known that he believed Bulger framed him for a Braintree murder he didn’t commit — the 1980 killing of Robert LaMonica.

He spent 36 years behind bars but was released last year after a judge ordered a new trial in his case. Prosecutors have said they won’t retry him.

“I think everybody in the world knew that Whitey screwed me,” Weichel told the Globe Wednesday.

Weichel couldn’t recall if he spoke about his theory with Geas. He added that he was shocked that Bulger, 89, was transferred to the same Hazelton penitentiary as Geas.

“I wouldn’t be surprised if this is a setup,” Weichel said about Bulger’s murder. “That’s a lot of coincidences there. I don’t believe in coincidences.”

Two years after his 2011 capture, Bulger handed over letters to Weichel’s attorneys that suggested another man was to blame in LaMonica’s death. But the aging Winter Hill Gang capo-turned-FBI informant refused to sign an affidavit or testify on his behalf, as requested by Weichel’s lawyers.

Daniel Kelly, a lawyer who’s represented Geas and maintains a friendship with him, said Geas repeatedly spoke about how unfair he thought Weichel’s case was.

“He referenced that [Weichel] was framed,” Kelly told the Globe.

The lawyer said he didn’t know whether Geas was involved in Bulger’s murder.

But he said a Globe report saying that he refused to identify anyone else involved in the fatal beatdown sounded just like his friend.

“Freddie [Geas] was a stand-up guy, the last of the Mohicans,” Kelly said.

Also raising eyebrows is who else is locked up in Hazelton: Paul Weadick and former New England Mafia capo Francis “Cadillac Frank” Salemme, who were recently convicted for the 1993 slaying of a Boston nightclub owner.

Salemme notably testified against Bulger’s cohort, corrupt FBI agent John Connolly.

Weadick’s lawyer, Mark Shea, insisted Weadick was not a suspect in Bulger’s murder.

He said the beating death of Bulger was “a despondent act of someone with nothing left to lose, and that’s not how I view Paul Weadick.”

The Federal Bureau of Prisons has so far been mum on Bulger’s murder. Sources told The Post the wheelchair-bound gangster was attacked by more than one inmate, including one who used a padlock wrapped in a sock to bludgeon him.