Apple CEO Tim Cook on Thursday announced he's gay.

“I'm proud to be gay, and I consider being gay among the greatest gifts God has given me,” Cook wrote in an essay published in Bloomberg Businessweek.

The 53-year-old Cook has previously kept quiet about his personal life.

“I don't consider myself an activist, but I realize how much I've benefited from the sacrifice of others,” he added. “So if hearing that the CEO of Apple is gay can help someone struggling to come to terms with who he or she is, or bring comfort to anyone who feels alone, or inspire people to insist on their equality, then it's worth the trade-off with my own privacy.”

The announcement uniquely situates Cook as the only openly gay CEO in the S&P 500, according to John Browne, the former CEO of British oil giant BP who was forced to resign in 2007 after being outed. In promoting his recent book, The Glass Closet: Why Coming Out is Good for Business, Browne stated, “If you look at the S&P 500, there isn't one out gay CEO.”

While quiet about his sexuality, Cook has been a vocal supporter of gay rights, in particular laws that prohibit workplace discrimination based on sexual orientation and gender identity.

(Related: Apple's Tim Cook calls on House to pass gay protections bill ENDA.)