It was the bald head that became the avatar of a million dreamy rebellions; the shaved pate that bridged the gap between the angry and the sublime. It is almost impossible to think about Sinead O’Connor, the Irish singer whose death was reported on July 26, or her work, without thinking about her hair. Or lack of it.

Without thinking about the striking curve of her shorn skull on the cover of her 1987 debut album, “The Lion and the Cobra,” her face below caught mid-scream; the nakedness it seemed to convey in the 1990 video of “Nothing Compares 2 U,” as her blue eyes brimmed with tears; the purity of the line on the cover of her 2021 memoir, “Rememberings.” Which contains an entire chapter entitled “Shaving My Head.”

It was effectively her signature — in a 2014 story in Billboard Ms. O’Connor, 56 when she died, identified herself as “the bald woman from Ireland” — along with her Dr. Martens and torn jeans, and it followed her throughout her life, just as much as her ripping up the photo of the Pope on “Saturday Night Live” in 1992 did. Even in the few periods when she grew her hair back, she was often referred to as the “formerly bald” Sinead O’Connor. And as such, she was an integral part of the renegotiation of old stereotypes of gender, sexuality, rebellion and liberation that is still going on today.

“I just don’t feel like me when I have hair,” she told The New York Times in 2021.

Now that female baldness has become more common, has become a badge of identity for women such as Ayanna Pressley, the representative from Massachusetts who went public with her alopecia in 2020, and X González, the Marjory Stoneman Douglas High School student (then known as Emma) who became a campaigner for gun control, not to mention the Dora Milaje of “Black Panther,” it can be hard to remember how extraordinary it was when Ms. O’Connor emerged.

But that seeming repudiation of her own porcelain beauty in the wake of a spate of teen pop queens, at a time when armoring yourself in a helmet of big hair was a big thing and shaving your head was still largely seen as a punishment, was as much of a statement of singularity as her sound.

Perhaps, it was also the first sign of the controversial politics to come, including refusing to play the national anthem before her concerts and stenciling the logo of Public Enemy into the side of her head at the 1989 Grammys when the show’s organizers declined to televise the first-ever award for Best Rap Performance.

She offered various explanations of the choice. All the stories come down to the same thing in any case, which was a refusal to cater to traditional definitions of “pretty” as established by the male gaze as long ago as Rapunzel and Lady Godiva.

In shearing her head “she was literally shearing away a false narrative,” said Allyson McCabe, the author of “Why Sinead O’Connor Matters.”

In 1991 Ms. O’Connor told Spin, “shaving my head to me was never a conscious thing. I was never making a statement. I just was bored one day and I wanted to shave my head, and that was literally all there was to it.” However, she also said, “The women who are admired are the ones that have blond hair and big lips and wear red lipstick and wear short skirts, because that’s an acceptable image of a woman.” And, “Because I have no hair, people think I’m angry.”

In a 2017 TV interview she told Dr. Phil that it was because during her abusive childhood her mother had compared her with her sister, who had long red hair, unlike Sinead. “When I had long hair, she would introduce us as her pretty daughter and her ugly daughter,” Ms. O’Connor said in the interview. “And that’s why I cut my hair off. I didn’t want to be pretty.”

In the interview she also said, “It’s dangerous to be pretty, too, because I kept getting raped and molested everywhere I went,” and “I did not want to dress like a girl. I did not want to be pretty.”

In her memoir, she wrote that she was working on her first album in London, and had been told by a male music executive she should grow her (buzzed but not shorn) hair long and start to dress more like a girl. The next day she went to a barbershop and had it all shaved off.

During the period after the “S.N.L.” appearance, when she was rejected by the music industry and revealed she had been diagnosed as bipolar, Ms. O’Connor’s bald head was taken as a sign of instability (just as it was later with Britney Spears). The fact that she continued shaving her skull for the rest of her life suggested it was, rather, a sign of selfhood.

The first time she looked in the mirror after that visit to the barbershop, she wrote in the book, “I looked like an alien.” Another way to put it, however, is she looked like the woman she became. And in becoming that woman — in giving herself that permission — she helped extend it to us all.