Fifty years after “Cabaret” made her a superstar, Liza Minnelli lives a quiet life in an apartment in West Hollywood.

At 76, and with enough headlines behind her for three lifetimes, the singer and actress is rarely seen in public.

But in what would prove to be the second most surprising moment at March’s Oscars, the icon joined Lady Gaga to hand out the Best Picture award — and her frail appearance and confused demeanor was a shock to many.

Now in a wheelchair after battling years of ill health, an emotional Minnelli was given a standing ovation by the A-list audience.

“Oh! It’s so exciting,” Minnelli exclaimed as Gaga — who had stepped away to allow her a moment in the sun  — told her: “You see that? The public, they love you.”

It was Minnelli’s former publicist Scott Gorenstein who helped make the moment happen, after he was approached by Academy officers who said that Gaga personally asked that the actress present with her in honor of the anniversary of “Cabaret.”

“Liza is living her best life, not having to be in front of the cameras,” Gorenstein told The Post. “She’s been under tremendous pressure her entire life to perform for audiences. The past couple of years have allowed her to relax and enjoy another phase of her life.

“She has had some health problems. However, when an opportunity comes in front of me that says ‘Would Liza Minnelli like to present the Best Picture Oscar with Lady Gaga?’ the quiet life goes out of the window! Liza is a legend and she deserves to be at the Academy Awards, so I put it in front of her people and recommended that she do it,” he added “I said it would be an historic occasion.

“I wanted to remind people who she is,” he added.

Minnelli was to be the big surprise of the evening — until Will Smith slapped host Chris Rock onstage.

“Unfortunately, Will Smith stole a little bit of that thunder,” Gorenstein said. “But Liza earned every bit of that ovation. They were standing for her, for her mother and for her father. There was a lot of history in that moment.”

Minnelli’s life is the stuff of Tinseltown legend. Born to “The Wizard of Oz” actress Judy Garland and director Vincente Minnelli — and named after the Ira Gershwin song “Liza (All the Clouds’ll Roll Away),” she made her silver screen debut as a toddler alongside her mom in 1949’s “In the Good Old Summertime.”

At 18, she performed with her mother at a London Palladium concert that was released as an album. A year later, Minnelli won a Tony for “Flora the Red Menace.”

She released a slew of records — usually standards and songs from musicals — and acted in such films as “New York, New York” (the title song would become her signature number) and “Tell Me That You Love Me, Junie Moon.” That one was notable because a nude scene filmed in a Massachusetts graveyard led to what was known as the “Liza Minnelli Bill” and prohibited filming in that state’s cemeteries without permission. 

Her role as the tragic Sally Bowles in “Cabaret” would sear her gamine image into pop-culture history, and her TV special “Liza With A ‘Z’” meant no one would mispronounce her name again.

She is just one of a handful of people to win an EGOT — an Emmy, Grammy, Oscar and Tony — although Gorenstein pointed out that the Kennedy Center has yet to bestow an honor on her, which has created online grumbling from her fans for years.

But Minnelli’s life has been marked by pain. She has been married and divorced four times, suffered three miscarriages (she has no children), and talked openly about her struggles with substance abuse.

“My whole life, this disease has been rampant,” she told The Guardian of her alcoholism in 2008. “I inherited it, and it’s been horrendous, but I have always asked for help.”

Her mother suffered tremendously from alcohol and drug problems. It was said that Garland began using barbiturates and amphetamines as a teenager, to help her stay peppy, sleep and stay slim as she made such movies “The Wizard of Oz,” “Babes in Arms” and the Andy Hardy franchise with Mickey Rooney.

Garland was a full-on alcoholic and drug addict by age 30, when Liza was just 6 years old.

When her mother died in 1969, at just 45, Minnelli was prescribed Valium to help deal with her grief. It led to her own abuse of prescription drugs and alcohol. In his diaries, Andy Warhol noted that she arrived at fashion designer Halston’s home in 1978 and said, “Give me every drug you’ve got.”

Minnelli had the first of multiple trips to rehab in 1985.

“So what do you do?” she asked on the “Today” show in 2005 after a relapse. “You get up and you go on, and you try not to do it again.”

In 2000, Minnelli was admitted to the ICU at a Florida hospital with partial paralysis, slurred speech and drooping facial muscles. She was diagnosed with viral encephalitis and, at the time, a doctor said that “she was quite sick and was in very serious condition” when she came in. 

“I couldn’t walk and I couldn’t talk, and they told me I wouldn’t … ever again,” she told NBC. “After I was told that, everybody left the room and I turned my face to the wall and started to go ‘A – B – C.’ You know, that’s what it felt like because I had Carnegie Hall to rehearse. I want to live. I have always wanted to live.”

In 2015, Minnelli sold her Upper East Side co-op for $8.37 million and moved to the West Coast, leaving behind Gorenstein and longtime assistant Nicole Guest, who were, he said, both deeply devoted to her and devastated by her departure.

But they no longer have direct contact with Minnelli. Multiple sources added that many from Liza’s old life in New York City have lost touch with her.

“There are definitely people [in New York City] who love Liza, who miss her,” Gorenstein said.. “We want her to be healthy and we worry that there is no one around [in LA] to look after her like we would in New York.”

She is believed to have caretakers who help her. One of her closest friends is pianist and performer Michael Feinstein, whom she discovered playing in a piano bar in NYC in the 1980s.

“Liza is someone who would admit to being needy. She’ll say, ‘Do this for me, honey,’” one showbiz insider told The Post. “When she moved out to LA, she reached out to Michael and he’s helped take control of her life.”

In January, Feinstein and Minnelli appeared together on CBS “Sunday Morning,” chatting with Jane Pauley, who asked Minnelli:  “Do you recognize that you have achieved the status of legend?”

“No, I have to be told a lot,” Minnelli replied. “Like, I keep saying to Michael, ‘Is that all right?’ I had great people around me. The biggest thing I got was to recognize somebody else’s talent.”

Of her friendship with Feinstein, Minnelli said: “I mean, we met each other and we were joined at the hip.”

A rep for Feinstein told The Post, “Liza relies on Michael as anyone would a best friend of several decades and vice versa. They give each other advice and they are each other’s sounding board both in their personal and professional lives. They are, simply, family.”

Minnelli is currently working with Feinstein as executive producer of an upcoming album called “Gershwin Country,” and producing his new tour, celebrating Judy Garland’s 100th birthday in June, one of many projects around the world celebrating her centennial.

Asked about Minnelli’s relationship with her younger sister Lorna Luft, which has reportedly been rocky over the years, the showbiz insider said: “That whole ‘sisters don’t talk’ thing is bulls–t. Like any family relationship, they have their good moments, their bad moments. I happen to know that Lorna knew the Oscars moment was happening, Liza wanted Lorna to know, and [Lorna] would have been proud of it.”

Requests for comment were not returned by Luft’s reps.

At the Oscars, Minnelli appeared befuddled as she held up her cue cards and said “Now what am I? I don’t quite understand.” which prompted Gaga to hold her hand and say, “I got it.”

When Minnelli stumbled as she began to introduce the nominees, Gaga jumped in to finish her sentences as the films played in the montage. Gaga was heard whispering, “I gotcha,” as an appreciative Minnelli laughed and they held hands.

“I know,” Minnelli replied, before announcing “CODA” as the winner.

“I have to give a lot of props to Gaga,” said Gorenstein, referencing how the singer recorded and performed with Tony Bennett, who now has Alzheimer’s. The two recorded the TV special “One Last Time: An Evening With Tony Bennett and Lady Gaga,” said to be his last performance, in 2021. “We all know how dear she has been to Tony Bennett and she really respects talent and I knew that Liza would be in great hands.”

Gaga has made it no secret that she considers Minnelli to be a hero. The pair first met when Gaga invited Minnelli to a concert at Madison Square Garden, filmed for HBO, back in 2011.

Gaga told the crowd how her teachers at NYU’s Tisch School of the Arts, had told her she didn’t have what it took to “be a superstar.”

“You’ll never be the main character… the blonde … your hair’s too dark … you look too ethnic,” she recalled being told — to which she would reply, “What about Liza?” She then asked the audience to give a thrilled Minnelli a standing ovation.

Despite seeming frail, Minnelli is still able to put her famous talent to use.

Giving viewers a treat of a performance of “I Love A Violin” on CBS last month, Minnelli said wistfully: “When I’m singing to an audience, I’m not singing to an audience, I’m singing to you …What I wanna say to the audience is, ‘Have you ever felt like this? ‘Cause it’s what I’m going through now.’ I just want people to know I’ve been through what they’ve been through.”