In a written statement, Apple, the world's second biggest company by market capitalization, announced that chief operating officer Tim Cook would take over as CEO but that Jobs would stay on as chairman of the board.
"Steve's extraordinary vision and leadership saved Apple and guided it to its position as the world's most innovative and valuable technology company," board member Art Levinson said in a statement.
No reason was given for Job's resignation, but his health problems, including a lengthy medical leave for a liver transplant in 2009 and his increasingly gaunt appearances at public events, fueled speculation he would have to give up the everyday running of the company he co-founded in 1976.
Cook ran Apple when Jobs went on medical leave and has essentially been running day-to-day operations since early this year with the company racking up record revenue and profit.
Jobs is seen as the heart and soul of Apple, with analysts and investors repeatedly expressing concern over how