Like many parents, Yvonne Meré was deeply disturbed when she read about a frightening new trend.

Boys were using “nudification” apps to turn photos of their female classmates into deepfake pornography, using images of the girls’ faces, from photos in which they were fully clothed, and superimposing them onto images of naked bodies generated by artificial intelligence.

But unlike many parents who worry about the threats posed to their children in a world of ever-changing technology, Ms. Meré, the mother of a 16-year-old girl, had the power to do something about it. As the chief deputy city attorney in San Francisco, Ms. Meré rallied her co-workers to craft a lawsuit, filed in state court on Wednesday night, that seeks to shut down the 16 most popular websites used to create these deepfakes.

The legal team said it appeared to be the first government lawsuit of its kind aimed at quashing the sites that promote the opportunity to digitally “undress” women and girls without their consent.

After reading a New York Times article about the tremendous damage done when such deepfake images are created and shared, Ms. Meré texted Sara Eisenberg, the mother of a 9-year-old girl and the head of the unit in the city attorney’s office that identifies major social problems and tries to solve them through legal action. The two of them then reached out to the office’s top lawyer, City Attorney David Chiu.

“The article is flying around our office, and we were like, ‘What can we do about this?’” Mr. Chiu recalled in an interview. “No one has tried to hold these companies accountable.”

Several states have enacted measures criminalizing A.I.-generated sexually explicit depictions of minors, but Mr. Chiu says that requires going after the people creating and distributing the images, one by one. The new lawsuit out of San Francisco asks a judge to order the sites used to create the content to shut down altogether.