Written By: Ben Cosgrove

On July 5, 1946, less than a week after the United States detonated an atomic bomb above tiny Bikini Atoll in the South Pacific, a Frenchman named Louis Réard an automobile engineer moonlighting as a fashion designer introduced to the sunbathing public what was billed as the world’s smallest swimsuit. Réard called his creation the bikini a name inspired, he later said, by the sight of women rolling up their bathing suits in order to acquire a more complete tan.

Two-piece swimsuits had, of course, been around for a long, long time before Réard came along. Greek urns and mosaics created more than 3,000 years ago depict women athletes wearing two-piece outfits. But Réard’s genius was to devise a garment, out of as little fabric as possible, that one could still legally wear in public.

He marketed his new fashion brilliantly, as well—pronouncing, for example, that a bathing suit wasn’t a true bikini unless both pieces could be pulled through a wedding ring.

Here, LIFE.com offers a celebration of a bathing staple that, through the years, has enjoyed and endured a dizzying array of permutations while always remaining, unmistakably, itself.

Some of the early photos in this gallery depict two-piece bathing suits that might, at first glance, look like bona fide bikinis—but, in Réard’s eyes, would not fit the bill. After all, can be wearing a genuine bikini if, say, one’s bellybutton is covered by a swath of nylon, no matter how elegant or tasteful that swath might be.

Bikinis are not for everyone. There are, thankfully, as many styles of bathing suit as there are human body types and temperaments. That said, it remains incontestably true that few sights can evoke thoughts of summer’s delights with quite the same visceral punch as the unmistakable silhouette of Monsieur Réard’s ingeniously simple, timeless design.

Model June Pickney, 1960.

Stan Wayman/Life Pictures/Getty Images

Actress Linda Christian in 1945.

Bob Landry/Life Pictures/Getty Images

Sunbathing in France, 1945.

Ralph Morse/ Life Pictures/Getty Images

Actress Dona Drake playfully took aim with a rifle on the balcony of her Los Angeles home, 1942.

Peter Stackpole/Life Pictures/Getty Images

Model Lynn Jones, 1955.

Peter Stackpole/Life Pictures/Getty Images

French actress Barbara Lange in a makeshift two-piece bathing suit she cut from one yard of cloth, 1945.

Nina Leen/Life Pictures/Getty Images

Santa Monica, Calif., 1940.

Peter Stackpole/Life Pictures/Getty Images

This sun bather had creative tattoos, 1941.

Peter Stackpole/Life Pictures/Getty Images

Rita Hayworth at home in Los Angeles, 1945.

Peter Stackpole/Life Pictures/Getty Images

Florida, 1945.

Nina Leen/Life Pictures/Getty Images

Florida, 1945.

Nina Leen/Life Pictures/Getty Images

Florida, 1945.

Nina Leen/Life Pictures/Getty Images

Sunbathing in France, 1945.

Ralph Morse/Life Pictures/Getty Images

Sunbathing in France, 1945.

Ralph Morse/Life Pictures/Getty Images

Sunbathing in France, 1945.

Ralph Morse/Life Pictures/Getty Images

Sunbathing in France, 1945.

Ralph Morse/Life Pictures/Getty Images

Beauty pageant winner Jackie Lee Barnes posed poolside in Albuquerque, New Mexico, in 1949.

Ed Clark/Life Pictures/Getty Images

Model in a bikini, 1950.

Ed Clark/Life Pictures/Getty Images

Model in a bikini, 1950.

Ed Clark/Life Pictures/Getty Images

French fashion model Christiane Richard wore a bikini while drinking her morning coffee, 1950.

Nat Farbman/Life Pictures/Getty Images

Jayne Mansfield posed with hot-water bottle likenesses floating around her, 1957.

Allan Grant/Life Pictures/Getty Images

Jayne Mansfield and unidentified man, 1961.

Stan Wayman/Life Pictures/Getty Images

Skin diving in Israel, 1960.

Paul Schutzer/Life Pictures/Getty Images

Sunbathing, 1961.

Allan Grant/Life Pictures/Getty Images

Actress Philomene Toulouse, cradling a pet fox, vied for attention at the Cannes film festival, 1962.

Paul Schutzer/Life Pictures/Getty Images

Cannes, France, 1962.

Paul Schutzer/Life Pictures/Getty Images

Atlantic City, New Jersey, 1964.

Art Rickerby/Life Pictures/Getty Images

Hungarian model, 1965.

Walter Sanders/Life Pictures/Getty Images

Model Naty Abascal showed off designs on her chest and stomach, Bahamas, 1968.

Bill Eppridge/Life Pictures/Getty Images

Near Malibu, California, 1970.

Co Rentmeester/Life Pictures/Getty Images

Southern California, 1970.

Co Rentmeester/Life Pictures/Getty Images

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