The monster who killed and chopped up 8-year-old Leiby Kletzky more than a decade ago — in one of the Big Apple’s most infamous child abduction and murder cases — died behind bars, The Post has learned.

Levi Aron, 49, died shortly before 10:30 a.m. Wednesday at a hospital near Wende Correctional Facility in Erie County, state correction officials confirmed.

The twisted killer was serving 40 years to life for little Leiby’s brutal 2011 murder.

Aron admitted that he abducted the boy just blocks from his Borough Park home on July 11, 2011, took him to a wedding in Rockland County then returned home to learn a massive search was underway for the missing child.

Panicked, he drugged the youngster, smothered him with a towel, chopped up his body and dumped the remains, Brooklyn prosecutors said at his bombshell trial the following year.

“I went for a towel to smother him in the side room,” the deranged murderer confessed after his arrest. “He fought back a little bit but eventually he stopped breathing.

“I was still in panic from the fliers and afraid to bring him home.”

The horrific crime rocked Brooklyn’s Orthodox Jewish community and sent shockwaves across the city.

The slain youngster’s father, Nachman Kletzky, declined to comment when reached by The Post Thursday.

The grieving dad sued the killer and his father in August 2011 for $100 million each, seeking punitive damages while calling the crime “utterly reckless, malicious and wanton.”

Aron, who was convicted on murder and kidnapping charges, was taken from the prison to a nearby hospital on Aug. 23 “for a medical condition,” a spokesman for the state Department of Correction and Community Supervision said Thursday.

The killer’s family has asked for an autopsy to be performed, the spokesman said.