Sinead O’Connor, the outspoken Irish singer-songwriter best known for her powerful, evocative voice, as showcased on her biggest hit, a breathtaking rendition of Prince’s “Nothing Compares 2 U,” and for her political provocations onstage and off, has died. She was 56.

Her family announced the death in a statement, according to the BBC and the Irish public broadcaster RTE. “It is with great sadness that we announce the passing of our beloved Sinead,” the statement said. “Her family and friends are devastated and have requested privacy at this very difficult time.” No other details were provided.

Recognizable by her shaved head and by wide eyes that could appear pained or full of rage, Ms. O’Connor released 10 studio albums, beginning with the alternative hit “The Lion and the Cobra” in 1987. She went on to sell millions of albums worldwide, breaking out with “I Do Not Want What I Haven’t Got” in 1990.

That album, featuring “Nothing Compares 2 U,” a No. 1 hit and MTV staple, won a Grammy Award in 1991 for best alternative music performance — although Ms. O’Connor boycotted the ceremony over what she called the show’s excessive commercialism.