(Screenshot via YouTube.)

Playboy founder Hugh Hefner died from natural causes at his home, the Playboy Mansion, on Wednesday. He was 91.

A pioneer for the straight sexual liberation movement, Hefner was also one of the early advocates for gay rights tracing back to the 1950s.

The 2009 documentary “Hugh Hefner: Playboy, Activist and Rebel,” explains that Hefner stood up for gay representation dating back to 1955. Esquire had rejected “The Crooked Man,” a science fiction story written by Charles Beaumont.

“The Crooked Man” told the story of a world where heterosexuals were the minority and punished while homosexuals were the majority. Hefner accepted the story to run in Playboy and received an onslaught of angry letters.

“If it was wrong to persecute heterosexuals in a homosexual society then the reverse is wrong too,” Hefner reportedly wrote back.

Hefner also was one of the first to stand up for transgender rights. In the 1980s, transgender model Caroline “Tula” Cossey was outed by the tabloid News of the World. Hefner put Cossey on the cover of Playboy making her the first transgender model to grace Playboy.

He kept his stance on gay rights years later when he told the Daily Beast in 2009 that nothing was wrong with gay marriage.

“Without question, love in its various permutations is what we need more of in this world,” Hefner said. “The idea that the concept of marriage will be sullied by same-sex marriage is ridiculous. Heterosexuals haven’t been doing that well at it on their own.”

Hefner is survived by his wife Crystal and four children.

American Icon and Playboy Founder, Hugh M. Hefner passed away today. He was 91. #RIPHef pic.twitter.com/tCLa2iNXa4

— Playboy (@Playboy) September 28, 2017