The mob’s gambling racket is about to sleep with the fishes.

The US Supreme Court’s sports-betting ruling dealt a losing hand to organized crime in the New York area, legal experts said Monday.

Gambling and loan-sharking have traditionally been the mob’s “bread and butter,” and the decision will “significantly reduce” its clientele, former federal prosecutor Thomas Seigel said.

“They will definitely lose a regular source of predictable income,” said Seigel, who ran the Organized Crime and Gangs Section of the Brooklyn US Attorney’ s Office.

Defense lawyer John Meringolo, who’s represented John “Junior” Gotti and reputed Philadelphia mob boss Joseph “Skinny Joey” Merlino, said legal sports betting “will have a detrimental effect on the mob and anyone who tries to make a living through this type of vice.”

“For what’s left of what they do, this would significantly hurt their bottom line, if not completely destroy it,” said Meringolo, also a Pace Law School professor.

“If there’s no gambling, there’s no core business.”

Seigel — who prosecuted crooked NBA referee Tim Donaghy on gambling charges — said he expected mobsters would come up with new scams, potentially involving crypto-currencies in an “analog to the penny stocks of the ’90s.”

“I wouldn’t fully count them out, because they are resilient, but it is definitely going to be a blow,” he said.