The poster is yellow. A naked woman reclines on plush, red fabric. Half her right breast is visible. Her left foot rests gently on her right calf. She is famous, this woman with the long bare back. Her body is lifted from “Grande Odalisque” and has been lounging at the Louvre for years. But on this yellow poster, there is something different about her.

She has the head of a gorilla.

Above her body is the question: “Do women have to be naked to get into the Met. Museum?”

“Less than 3% of the artists in the Modern Art sections are women,” the sign continues, “but 83% of the nudes are female.”

The gorilla, teeth bared and nostrils flared, snarls at the words. There are more gorillas where she came from. In fact, there is an entire organization of them: the Guerrilla Girls.

Guerrilla Girl Kathe Kollwitz. (© Lynn Hershman)

They call themselves “feminist masked avengers.” The Guerrillas create art designed to hold society accountable for its sexist or racist dealings, and they do so anonymously, using the names of dead female artists as pseudonyms and wearing gorilla masks whenever they appear in public.

These are women who refuse to accept the exclusivity of the art establishment, who believe their empowering mantra deserves a medium worthy of their message.

They could be anyone, anywhere. They’re diverse in almost every way except profession; most Guerrillas are visual artists. Right now, their work is on display at the National Museum of Women in the Arts. The exhibit, “Guerrilla Girls Talk Back,” opened June 17.

Kathryn Wat, curator of modern and contemporary art at the museum, said the Guerrilla Girls exhibit affects visitors in a way that is “incredibly gratifying. . . . Guerrilla Girls make [people] think about something aside from the aesthetics.’’

The co-founders of the Guerrilla Girls, called “Frida Kahlo” and “Kathe Kollwitz,” were inspired in 1984 after seeing an exhibit at the Museum of Modern Art billed as a collection of the world’s most important contemporary work. Of the 169 artists represented, 17 were women. “Kahlo” and “Kollwitz” participated in a demonstration outside MoMA.

“We saw immediately that the protest had absolutely no effect on passersby,” Kollwitz said. “We realized there had to be a better way — a more media-savvy, more transgressive way — to get people’s attention and change their minds.”

They formed the Guerrilla Girls in the spring of 1985 in New York City, where they are still based.

The Guerrillas originally elected to be anonymous to protect their art careers. “We quickly realized that our anonymity was one of the secrets of our success because it kept the focus on the message, not on our personalities,” Kollwitz said.

Irina Aristarkhova, an assistant professor of women’s studies and visual art at Pennsylvania State University, uses “The Guerrilla Girls’ Bedside Companion to the History of Western Art” as a textbook in two courses. “The work of Guerrilla Girls represents a ‘total package’ for an educator,” Aristarkhova said in an e-mail. “Guerrilla Girls do to the art world what Jon Stewart or Stephen Colbert do to the news media.”

What started as an attack on the art world grew to encompass film and politics. In the 1990s, the Guerrillas made posters about reproductive rights and women in the military. A billboard near the Kodak Theatre during the 2002 Academy Awards displayed, “The Anatomically Correct Oscar. He’s white & male, just like the guys who win!”

Mary Boone was one of many art dealers the Guerrilla Girls targeted in the late 1980s for what they saw as an underrepresentation of female artists.

“No gallery showed enough women,” Boone said, more than 20 years later, “my gallery included.”

Still, she said the “relentlessness” of the Guerrilla Girls “was positive. They did provide a platform for change. I think the Guerrilla Girls provided an important vehicle for people to recognize that there was inequality.”

As Kahlo put it: “People do think that the art world is a meritocracy, [but] the art world is subject to the same forces as the rest of the world.”

Added Kollwitz: “We’ve always felt is a lot of discrimination is conscious, but a lot is unconscious, too. The stereotype of the genius artist is decidedly male.

“No one is against these art stars. We’re just afraid: Are museums going to have the real story of our culture?”

While museums initially reacted to the Guerrillas with, as Kahlo described, “disbelief and horror,” the Guerrillas are now beloved by the very institutions they’ve spent two decades fighting.

The Guerrillas were included in the “Elles@centrepompidou” exhibition at the Pompidou in Paris from May 2009 through this past February. Their work is currently on display at the Tate Modern in London, as it was in 2006 and 2007.

“We’re suddenly the darlings of museums,” said Kollwitz, sounding a little in awe. “It’s been great to get these huge audiences, but it’s confusing to a Guerrilla.”

Those audiences span the globe. The Guerrillas get thousands of letters a year, with return addresses ranging from Thailand to Brazil, expressing gratitude for their activism.

The art world “really has changed,” said Wat, the curator. “And I do believe that the Guerrilla Girls have been a catalyst for that change.”

Said Kollwitz: “By doing it in our crazy way, we created something that’s hard to deny and hard to forget. That’s our goal.”

So where do the Guerrillas fall in the grand tradition of masked avengers?

“We love to think of ourselves like Wonder Woman,” Kahlo said. “Or Batman.”

Guerrilla Girls Talk Back

through Oct. 2 at the National Museum of Women in the Arts, 1250 New York Ave. NW. Visit www.nmwa.org or call 202-783-5000.