LONDON >> Sinéad O’Connor, the gifted Irish singer-songwriter who became a superstar in her mid-20s and was known as much for her private struggles and provocative actions as for her fierce and expressive music, has died at 56.

“It is with great sadness that we announce the passing of our beloved Sinéad. Her family and friends are devastated and have requested privacy at this very difficult time,” the singer’s family said in a statement reported Wednesday by the BBC and RTE. No cause was disclosed.

She was public about her mental illness, saying that she was diagnosed with bipolar disorder. O’Connor posted a Facebook video in 2017 from a New Jersey motel where she had been living, saying that she was staying alive for the sake of others and that if it were up to her, she’d be “gone.”

When her teenage son Shane died by suicide last year, O’Connor tweeted there was “no point living without him” and she was soon hospitalized.

Recognizable by her shaved head and with a multi-octave mezzo soprano of extraordinary emotional range, O’Connor began her career singing on the streets of Dublin and soon rose to international fame.

She was a star from her 1987 debut album, “The Lion and the Cobra,” and became a sensation in 1990 with her cover of Prince’s ballad “Nothing Compares 2 U,” a seething, shattering performance that topped charts from Europe to Australia and was heightened by a promotional video featuring the gray-eyed O’Connor in intense close-up.

She was a lifelong non-conformist — she said she shaved her head in response to record executives pressuring her to be conventionally glamorous — but her political and cultural stances and troubled private life often overshadowed her music.

A critic of the Roman Catholic Church well before allegations of sexual abuse were widely reported, O’Connor made headlines in October 1992 when she tore up a photo of Pope John Paul II while appearing on NBC’s “Saturday Night Live” and denounced the church as the enemy.

The next week, Joe Pesci hosted “Saturday Night Live,” held up a repaired photo of the Pope and said if he had been on the show with O’Connor he “would have gave her such a smack.” Days later, she appeared at an all-star tribute for Bob Dylan at Madison Square Garden and was immediately booed. She was supposed to sing Dylan’s “I Believe in You,” but switched to an a cappella version of Bob Marley’s “War,” which she had sung on “Saturday Night Live.”

Although consoled and encouraged on stage by her friend Kris Kristofferson, she left and broke down, and her performance was kept off the concert CD. (Years later, Kristofferson recorded “Sister Sinead,” for which he wrote, “And maybe she’s crazy and maybe she ain’t/But so was Picasso and so were the saints.”)

She also feuded with Frank Sinatra over her refusal to allow the playing of “The Star-Spangled Banner” at one of her shows and accused Prince of physically threatening her. In 1989 she declared her support for the Irish Republican Army, a statement she retracted a year later. Around the same time, she skipped the Grammy ceremony, saying it was too commercialized.

In 1999, O’Connor caused uproar in Ireland when she became a priestess of the breakaway Latin Tridentine Church — a position that was not recognized by the mainstream Catholic Church. For many years, she called for a full investigation into the extent of the church’s role in concealing child abuse by clergy. In 2010, when Pope Benedict XVI apologized to Ireland to atone for decades of abuse, O’Connor condemned the apology for not going far enough and called for Catholics to boycott Mass until there was a full investigation into the Vatican’s role.

“People assumed I didn’t believe in God. That’s not the case at all. I’m Catholic by birth and culture and would be the first at the church door if the Vatican offered sincere reconciliation,” she wrote in the Washington Post in 2010.

O’Connor announced in 2018 that she had converted to Islam and would be adopting the name Shuhada’ Davitt, later Shuhada Sadaqat — although she continued to use Sinéad O’Connor professionally.