The monokini, designed by Rudi Gernreich in 1964, consisting of only a brief, close-fitting bottom and two thin straps, was the first women's topless swimsuit. His revolutionary and controversial design included a bottom that "extended from the midriff to the upper thigh" and was "held up by shoestring laces that make a halter around the neck." Some credit Gernreich's design with initiating, or describe it as a symbol of, the sexual revolution.

Gernreich designed the monokini as a protest against a repressive society. He did not initially intend to produce the monokini commercially, but was persuaded by Susanne Kirtland of Look to make it available to the public. When the first photograph of a frontal view of Peggy Moffitt wearing the design was published in Women's Wear Daily on June 3, 1964, it generated a great deal of controversy in the United States and other countries. Gernreich sold about 3,000 suits, but only two were worn in public. The first was worn publicly on June 22, 1964, by Carol Doda in San Francisco at the Condor Nightclub, ushering in the era of topless nightclubs in the United States, and the second at North Avenue beach in Chicago in July 1964 by artist's model Toni Lee Shelley, who was arrested.

Some manufacturers and retailers refer to modern monokini swimsuit designs as a topless swimsuit, topless bikini, or unikini.