LOS ANGELES • Hugh Hefner, the silk pyjamas-wearing founder of Playboy who helped steer nudity into the American mainstream, died on Wednesday at age 91.

Hefner, who in 1953 founded a trailblazing brand that would help usher in the 20th-century's shifting attitude towards sexuality, died peacefully in his Beverly Hills home.

A self-proclaimed master of marketing, his skill for self-promotion made it impossible to untangle his image from his empire.

He was reviled, first by guardians of the 1950s social order and later by feminists.

But Playboy's circulation reached one million by 1960 and peaked at about seven million in the 1970s.

His company branched into movie, cable and digital production, sold its own line of clothing and jewellery and opened clubs, resorts and casinos.

But the brand faded over the years and by 2015, the magazine's circulation had dropped to about 800,000.

Hefner remained editor-in-chief even after agreeing to the magazine's startling decision in 2015 to stop publishing nude photographs.

He handed over creative control of Playboy last year to his son Cooper and the magazine brought back nudes this year.

"My father lived an exceptional and impactful life as a media and cultural pioneer and a leading voice behind some of the most significant social and cultural movements of our time in advocating free speech, civil rights and sexual freedom," Cooper, 26, said.

Hefner was sometimes characterised as an oversexed Peter Pan as he kept a harem of young blondes that numbered as many as seven at his legendary Playboy Mansion.

He said that thanks to impotency-fighting drug Viagra, he continued exercising his libido into his 80s.

"I'm never going to grow up," he told CNN when he was 82.

"Staying young is what it is all about for me. Holding on to the boy and long ago, I decided that age really didn't matter and as long as the ladies... feel the same way, that's fine with me."

Hefner settled down somewhat in 2012 at age 86 when he took a woman, who was 60 years younger, as his third wife.

He said his swinging lifestyle might have been a reaction to growing up in a repressed family where affection was rarely exhibited.

He created Playboy as the first stylish glossy men's magazine.

In addition to nude fold-outs, it had intellectual appeal with top writers such as Kurt Vonnegut, Joyce Carol Oates, Vladimir Nabokov, James Baldwin and Alex Haley for men who said they did not buy the magazine just for the pictures.

In-depth interviews with historic figures such as Fidel Castro, Martin Luther King Jr, Malcolm X and John Lennon were featured regularly.

"I've never thought of Playboy quite frankly as a sex magazine," Hefner told CNN in 2002.

"I always thought of it as a lifestyle magazine in which sex was one important ingredient."

REUTERS, AGENCE FRANCE-PRESSE, NYTIMES