Plausibly the earliest gay icon was Saint Sebastian, a Christian saint and martyr, whose strong and shirtless physique, symbolic arrow-pierced flesh, and rapturous look of pain combined have intrigued artists, both gay and straight, for centuries and began the first explicitly gay cult in the nineteenth century. Richard A. Kaye, a journalist, wrote, "contemporary gay men have seen in Sebastian at once a stunning advertisement for homosexual desire (indeed, a homoerotic ideal), and a prototypical portrait of tortured closet case."
Due to Saint Sebastian's status as gay icon, Tennessee Williams chose to use that name for the martyred character Sebastian in his play, Suddenly, Last Summer. The name was also used by Oscar Wilde – as Sebastian Melmoth – when in exile after his release from prison. (wikipedia.org)
Kisihin Shinoyama, ‘Yukio Mishima as St. Sebastian’, 1966
Yomi Imoy, ‘San Sebastian (reloaded)’