Steve Jobs, the mind behind the iPhone, iPad and other devices that turned Apple into one of the world's most powerful companies, resigned as the company's chief executive, saying he can no longer handle the job.
The move appears to be the result of an unspecified medical condition for which he took an indefinite leave from his post in January. Apple's chief operating officer, Tim Cook, has been named chief executive.
In a letter addressed to Apple's board and the Apple community, Mr Jobs said he "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".
Apple said Mr Jobs was elected board chairman and Mr Cook is becoming a member of its board.
The company said Mr Jobs gave the board his resignation and suggested Mr Cook be named the company's new leader.
The January leave was Mr Jobs' third medical leave over several years. He had previously survived pancreatic cancer and received a liver transplant.
Mr Jobs' hits seemed to grow bigger as the years went on: After the colourful iMac computer and the now-ubiquitous iPod, the iPhone redefined the category of smart phones and the iPad all but created the market for tablet computers.
His own aura seemed part of the attraction. On stage at trade shows and company events in his uniform of jeans, sneakers and black mock-turtlenecks, he would entrance audiences with new devices, new colours, new software features, building up to a grand finale he would predictably preface by saying: "One more thing."
Mr Jobs, 56, shepherded Apple from a two-man start-up to Silicon Valley darling when the Apple II, the first computer for regular people to really catch on, sent IBM and others scrambling to get their own PCs to market.
After Apple suffered a slump in the mid-1980s, he was forced out of the company.
He was chief executive at Next, another computer company, and Pixar, the computer-animation company that produced Toy Story on his watch, during the 10 years before he returned.