Apple did not reveal where Jobs died or from what cause -- though in recent years he had fought pancreatic cancer and had a liver transplant.
"We are deeply saddened to announce that Steve Jobs passed away today," read a statement by Apple's board of directors. "Steve's brilliance, passion and energy were the source of countless innovations that enrich and improve all of our lives. The world is immeasurably better because of Steve. His greatest love was for his wife, Laurene, and his family. Our hearts go out to them and to all who were touched by his extraordinary gifts."
The homepage of Apple's website this evening switched to a full-page image of Jobs with the text, "Steve Jobs 1955-2011."
Clicking on the image revealed the additional text: "Apple has lost a visionary and creative genius, and the world has lost an amazing human being. Those of us who have been fortunate enough to know and work with Steve have lost a dear friend and an inspiring mentor. Steve leaves behind a company that only he could have built, and his spirit will forever be the foundation of Apple."
Jobs co-founded Apple Computer in 1976 and, with his childhood friend Steve Wozniak, marketed what was considered the world's first personal computer, the Apple II.
Shortly after learning of Jobs' death, Wozniak told ABC News, "I'm shocked and disturbed."
Industry watchers called him a master innovator -- perhaps on a par with Thomas Edison -- changing the worlds of computing, recorded music and communications.
Jobs rivals in the development of personal computers, Microsoft co-founders Bill Gates and Paul Allen, immediately reacted to his death and highlighted his importance to their industry.
Allen called him "a unique tech pioneer and auteur who knew how to make amazingly great products."
Gates also extended his condolences, and added via a written statement, "Steve and I first met nearly 30 years ago, and have been colleagues, competitors and friends over the course of more than half our lives.
"The world rarely sees someone who has had the profound impact Steve has had, the effects of which will be felt for many generations to come," he added. "For those of us lucky enough to get to work with him, it's been an insanely great honor. I will miss Steve immensely."
Jobs continued to innovate in recent years even as he battled severe health problems that prompted leaves of absence from Apple.
In 2004, he beat back an unusual form of pancreatic cancer, and in 2009 he was forced to get a liver transplant. After several years of failing health, Jobs announced on Aug. 24, 2011 that he was stepping down as Apple's chief executive.
"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," Jobs wrote in his letter of resignation. "Unfortunately, that day has come."