Steve Jobs has resigned from his position as Apple CEO, taking on the new role of chairman, according to a company-issued press release.
COO Tim Cook has been elected the company's new CEO, and will join the board as well.
"I have always said if there ever came a day when I could no longer meet my duties and expectations as Apple's CEO, I would be the first to let you know. Unfortunately, that day has come," Jobs wrote in his resignation letter. "I have made some of the best friends of my life at Apple, and I thank you all for the many years of being able to work alongside you."
He offered no specific reasons for his departure. While surprising in it's timing, the move was not entirely unexpected. Jobs is a survivor of pancreatic cancer who had a liver transplant in 2009, and has been on an indefinite leave of absence from the company since January.
Investors had been pressuring Apple for months to name some kind of leadership transition plan. Cook, who took over many of Jobs' keynote responsibilities at Apple events, has long been considered the likely successor.
Questions about Jobs' health will only intensify now that this move has been made. But taking on the role of chairman suggests that he is still capable of staying involved in company business.
"Steve's extraordinary vision and leadership saved Apple and guided it to its position as the world's most innovative and valuable technology company," said board member Art Levinson, chairman of Genentech, in the release. "Steve has made countless contributions to Apple's success, and he has attracted and inspired Apple's immensely creative employees and world class executive team. In his new role as Chairman of the Board, Steve will continue to serve Apple with his unique insights, creativity and inspiration."
As of 7:30 p.m. eastern time on Wednesday, Apple's stock was down 5.3% in after-hours trading.