Legendary Metropolitan Opera conductor James Levine molested an Illinois teenager from the time he was 15 years old, sexual abuse that lasted for years and led the alleged victim to the brink of suicide, according to a police report obtained by The Post.

The alleged abuse began while Levine was guest conductor at the Ravinia Music Festival outside Chicago, a post the wild-haired maestro held for two decades.

The alleged victim came forward to the Lake Forest, Ill. Police Department in October 2016 to detail the molestation, including times when Levine would masturbate in front of him and kiss his penis, according to the report.

The alleged victim informed a former Met Opera board member of the alleged abuse in 2016 and she alerted the Met’s general manager, yet Levine continued to wield his baton.

The now 74-year-old maestro, who spent 40 years as music director of the Metropolitan Opera and is currently director emeritus, conducted a performance of Verdi’s “Requiem” at Lincoln Center Saturday.

The alleged victim’s 2016 claims came nine years after the statute of limitations on a possible child sex crime in Illinois had expired. The age of consent in that state is 17. The Lake Forest Police Department investigated the allegations anyway, and turned its findings over to the Lake County State’s Attorney. A State’s Attorney spokeswoman told The Post Friday the case is still under review and no charges have been brought.

“I began seeing a 41-year-old man when I was 15, without really understanding I was really ‘seeing’ him,” the alleged victim, now 48, said in a written statement to the police department. “It nearly destroyed my family and almost led me to suicide. I felt alone and afraid. He was trying to seduce me. I couldn’t see this. Now I can.”

The alleged victim, whose name is being withheld by The Post, said Levine showered him with $50,000 in cash over the years.

In a statement to The New York Times, Peter Gelb, the general manager of the Met, said officials had already been aware of the allegations and will launch an investigation into Levine.

“This first came to the Met’s attention when the Illinois police investigation was opened in October of 2016,” Gelb said. “At the time Jim said that the charges were completely false, and we didn’t hear anything further from the police. We need to determine if these charges are true and, if they are, take appropriate action. We will now be conducting our own investigation with outside resources.”

Rumors about improper sexual contact have long swirled around Levine, who closely guards his private life. The pianist and musical prodigy made his debut at the Metropolitan Opera in 1971 at the age of 28 and within months became its main conductor.

Levine rose to music director at the Met in 1976 and held the title until April 2016. The Met paid him $1.8 million in 2015, according to its latest available tax filings.

He is considered a giant of the classical-music world, nominated for 37 Grammy Awards and winner of 10. He was honored by the Kennedy Center in 2002, alongside Elizabeth Taylor, Paul Simon, James Earl Jones and Chita Rivera. He conducted the Chicago Symphony Orchestra for Disney’s “Fantasia 2000” movie.

Throughout his long and distinguished career, Levine held posts — and picked up paychecks — with other orchestras, including music director of the Boston Symphony. That company paid Levine $1.2 million in 2010, his last year there.

The maestro made a splash in 1971 as a last-minute guest conductor with the Chicago Symphony at its summer home, the Ravinia Music Festival located in the city’s ritzy North Shore suburbs. The festival appointed him music director in 1973, a post he held for 21 years.

Earlier this year, Ravinia bestowed a new title on Levine — conductor laureate — and he is expected to lead concerts and hold master classes during two-week summer residencies through 2022.

It was at one such Ravinia concert in 1973 when the alleged victim, then a 4-year-old boy living in a nearby suburb, was taken backstage by his parents to meet the great maestro.

The boy would see the conductor during subsequent summer visits to the festival and, according to the police account he later gave as an adult, the older man “took an interest” in him, even sending conductors’ batons and other gifts to his home.

The alleged victim said he did not see Levine for several years starting at age 10 and met him again at 14 when he started going backstage at Ravinia on his own, according to the report.

In 1985, when the alleged victim was 15, he told police that Levine drove him home and stopped the car in the back section of his family’s driveway.

“He started holding my hand in a prolonged and incredibly sensual way,” writes the alleged victim. “I was not aroused as I never was during my relationship with him as I am a heterosexual individual. But there were some feelings of affection and mostly confusion. … I was very uncomfortable with the hand holding.”

During that encounter, Levine allegedly told the young man “I want to see if you can be raised special like me.” He also asked him to “Come to New York so I can audition you as a conductor.”

He said he later asked fellow students at a summer program, “Am I gay because he held my hand?” according to the report.

The alleged victim said that Levine first fondled his penis when he was around 16 years old. He said the alleged encounter happened at the Deer Path Inn in Lake Forest, Ill., 10 miles from the Ravinia Festival.

The luxury hotel, styled as an English inn, was the scene of “hundreds of incidents” over the years, according to the report.

The alleged victim said Levine would invite him to dinner, keep him waiting as to the appointed time, and then ask to meet him immediately at the Deer Path Inn, the report says.

The teen thought he was talking to his mentor about how to achieve his ambitions in classical music, according to the report.

“I would get there and the lights were off and he would say to me, after I came in, and after a hug, ‘Take off your clothes. I am working very hard and need to rest,’” the report says.

Levine would masturbate in the bed or in the bathroom, the alleged victim told police.

The maestro told the young man “Only with him … could I safely explore my feelings,” the report says.

In 1987, he said the alleged abuse escalated and Levine “put his finger in my anus,” according to the report.

That same year, Levine wrote the alleged victim a college recommendation letter on Met stationery, which is included in the police report, praising the young man and saying “over the years I have always found him to be exceptionally responsive and concentrated, curious and eager to learn.”

The alleged victim said his encounters with Levine continued until 1993, sometimes in New York City where they dined at Cafe des Artistes and Shun Lee on the Upper West Side near the Metropolitan Opera’s home at Lincoln Center.

In one instance in New York City, Levine “kissed my penis,” the alleged victim said. He also told police “he would fondle my penis many times,” the report says.

“Levine was not a person you ever said no to,” he told police.

The alleged victim said the abuse continued even after he was 18 because he had so much trust in Levine.

“He inflicted shame and guilt on me. Making [it] hard for me to see the wrong. Emotionally I have been hurt by this and confused and paralyzed,” he says in his statement to the police.

The alleged victim said he finally told his mother about the abuse in 1993.

In 2016, after contemplating going public, the alleged victim said he called a former board member at the Met who advised him to contact the police.

The board member, Beth Glynn, later told Lake Forest Police Detective Wendy Dumont that she spoke to the general manager of the Met about the victim’s phone call.

Glynn told Dumont there were “always rumors” about Levine “because he was socially awkward but he never had any issues at the Metropolitan Opera House for 40 years.”

When contacted by The Post, Glynn confirmed she urged the man “to call the police.”

Dumont also reached out to classical music blogger Greg Sandow, who told her he had been contacted by three men in past years purporting to have been abused by Levine, one of them being the alleged victim.

“The rumors of [Levine’s] alleged abuse have been widespread for decades and in my experience they seemed to be widely believed inside the classical music field though I’ve never heard anyone cite anything specific,” Sandow told the police.

Sandow declined to comment to The Post.

Levine himself acknowledged existence of these rumors in a 1987 New York Times article about management changes at the Met, but seemed to dismiss them.

He said 10 years earlier the Met’s general manager “called me about reports of a morals charge in Pittsburgh or Hawaii or Dallas. Both my friends and my enemies checked it out and to this day, I don’t have the faintest idea where those rumors came from or what purpose they served. Ron Wilford says it’s because people can’t believe the real story, that I’m too good to be true.’’

Wilford was Levine’s manager.

Levine went on to say that he was “not a doctor married with three children living in suburbia. I live my life openly; I don’t make pretenses of this or that. What there is is completely apparent, so if people want to damage me, they have to invent things that are lurid and vicious.’’

Levine has been hobbled in recent years by back problems and Parkinson’s disease. He lives at the famed San Remo apartment building on Central Park West where former oboist and Levine pal Sue Thompson was long his roommate.

Neither Levine nor his New York agent returned multiple requests for comment. A spokesman for the Met did not respond to repeated requests for comment. Its general manager, Peter Gelb, did not return a message.