A bikini is a type of women's bathing suit, characterized by two separate parts; one covering the breasts, the other the groin and buttocks, leaving an uncovered area between the two garments.

Two-piece garments worn by women for athletic purposes have been observed on Greek urns and paintings, dated as early as 1400 BC.

The modern bikini was invented by engineer Louis Reard in Paris in 1946 (introduced on July 5), and named after Bikini Atoll, the site of nuclear weapon tests in the Marshall Islands, on the reasoning that the burst of excitement it would cause would be like the atomic bomb.

Reard's suit was a refinement of the work of Jacques Heim who, two months earlier, had introduced the "Atome" (named for its size) and advertised it as the world's "smallest bathing suit". Reard split the "atome" even smaller, but could not find a model who would dare to wear his design. He ended up hiring Micheline Bernardini, a nude dancer from the Casino de Paris, as his model.

It took fifteen years for the bikini to be accepted in the United States. In 1951 bikinis were banned from the Miss World Contest. In 1957, however, Brigitte Bardot's bikini in And God Created Woman created a market for the swimwear in the US, and in 1960, Brian Hyland's pop song "Itsy Bitsy Teenie Weenie Yellow Polka Dot Bikini" inspired a bikini-buying spree. Finally the bikini caught on, and by 1963, the movie Beach Party, starring Annette Funicello and Frankie Avalon, led a wave of films that made the bikini a pop-culture symbol.

In recent years, the term monokini has come into use for topless bathing by women: where the bikini has two parts, the monokini is the lower part. Where monokinis are in use, the word bikini may jokingly refer to a two-piece outfit consisting of a monokini and a sun hat. The term was coined by Rudi Gernreich.

The tankini is a swimsuit combining a tank top and a bikini bottom.

The lower part of the bikini was further reduced in size in the 1980s to the Brazilian thong, where the back of the suit is so thin that it disappears into the buttocks. Recently bikinis have been getting smaller. This trend started with the top piece, but after shrinking the top so much that it barely covers the nipples, swimsuit manufacturers have moved on to reducing the size of the bottom piece. One can see the trend toward reduction in the following styles: slingshot (http://www.the-bikini.com/galleries-slingshot/), mini (http://www.the-bikini.com/galleries-mini/), teardrop (http://www.the-bikini.com/galleries-teardrop/), minimini (http://www.the-bikini.com/galleries-minimini/), micro (http://www.the-bikini.com/galleries-micro/), and, what could be called a double g-string, the minimicro (http://www.the-bikini.com/galleries-minimicro/).