Peggy Moffitt, a model and muse who famously posed in the designer Rudi Gernreich’s topless bathing suit, and whose bob and heavy eye makeup helped define the look of the 1960s, died on Saturday at her home in Beverly Hills, Calif. She was 86.

Her son, Christopher Claxton, said the cause was complications of dementia.

Ms. Moffitt started working with Mr. Gernreich as a fitting and show model in 1962. “I entertained myself and the audience by regarding the collection as a play, with each outfit a new act or a new character,” she wrote in “The Rudi Gernreich Book” (1991), a collaboration with her husband, the photographer William Claxton, who took the topless photo. “In fact, I didn’t really model the clothes so much as perform them.”

She met Mr. Gernreich when she was working at a small boutique in Beverly Hills that was known for its unusual and avant-garde clothes. Ms. Moffitt was drawn to the humor in his designs.

She was initially hesitant about posing for a photo in his topless suit, but she decided to do it as long as some conditions were met: that she never wear it in public and that Mr. Claxton, who was best known for his portraits of jazz musicians, shoot it.

The suit, made famous by Mr. Claxton’s 1964 picture, made international news when it was banned in some countries and denounced by the Soviet newspaper Izvestia; it said in its criticism that the American way of life “is on the side of everything that gives the possibility of trampling on morals and interests of society for the sake of ego.”

The photo continued to follow her for decades, and in the process became somewhat of a nuisance. “Think of something in your life that took one-sixtieth of a second to do,” she said in 2012. “Now, imagine having to spend the rest of your life talking about it. I think it’s a beautiful photograph, but, oh, am I tired of talking about it.”