"Let me be clear: I'm proud to be gay, and I consider being gay among the greatest gifts God has given me," he wrote in the essay, which was published in Bloomberg Businessweek.
Few corporate leaders have come out of the closet, even though doing so has become more common among celebrities, professional athletes and politicians. Gay rights supporters note that 29 states do not have laws that explicitly prohibit workplace discrimination based on sexual orientation, and they hope Cook's coming out will bring attention to the issue.
"When a CEO of a global company like Apple comes out, it opens the doors for LGBT employees around the world to be their authentic selves," said Selisse Berry, founder of the nonprofit Out & Equal Workplace Advocates. "It also paves the way for more out executives and CEOs to do the same; once the LGBT ceiling has been broken, it gives employees the freedom to put all their energy into their work without having to hide their personal lives."
Cook said that he had been open about his sexual orientation for years, and that plenty of colleagues at Apple have known that he's gay.
He said there wasn't a particular reason he chose to come out now, but that he thought about the question once posed by
"I often challenge myself with that question, and I've come to realize that my desire for personal privacy has been holding me back from doing something more important," Cook said. "That's what has led me to today."
In Silicon Valley, Cook's sexual orientation doesn't come as much of a surprise. The 53-year-old had been widely rumored to be gay for years, but the tech world largely paid little attention to such chatter.
That changed Thursday, with several tech leaders quickly turning to social media to applaud Cook's decision to come out.
"Thank you Tim for showing what it means to be a real, courageous and authentic leader," Facebook founder and CEO
"Inspired by @tim_cook," Microsoft CEO
Venture capitalist Marc Andreessen simply tweeted a link to Cook's essay along with one word: "Respect."
The question of Cook's sexuality was raised this year when, in June, a
The blunder drew an uncomfortable silence from the other hosts, before Hobbs said, "Oh, dear, was that an error? I thought he was open about it."
Cook didn't address the CNBC gaffe at the time, but he has long been vocal about his staunch support of gay rights.
Shortly after the CNBC incident, he tweeted: "Congrats to 5000 Apple employees/families who attended today's Pride parade. Inclusion inspires innovation. #applepride"
In July, he followed that up by tweeting a link to a video showing employees celebrating gay pride by donning white T-shirts with the Apple icon outlined by a rainbow.
And just this week, Cook slammed Alabama's long-standing issues with racial inequality and discrimination against gays in a speech he made during a ceremony inducting him into the Alabama Academy of Honor.
"There is little, if anything, that matters more in our country than our basic tenets of equality and human rights. I have long promised myself to never be silent in my beliefs in my regard to these tenets," Cook, who grew up in Robertsdale, Ala., said during the speech.
"As a state we took too long to take steps toward equality, and once we began, our progress was too slow. Too slow on equality for African Americans, too slow on interracial marriage, which was only legalized 14 years ago, and still too slow on equality for the LGBT community."
In his essay, Cook, who has been notoriously guarded about his privacy, said he would "like to hold on to a small amount of it." But he said he also knew coming forward could make a difference to those facing personal challenges.
"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," he said, "then it's worth the trade-off with my own privacy."