He passed away peacefully at his seaside home in Santa Cruz, California, with his family by his side, O'Neill's friends told KSBW news.
He opened his first surf shop in San Francisco in 1952, and popularised the use of the neoprene wetsuit for coldwater surfing.
His firm grew to become one of the world's biggest surfware brands. His son took over the business in 1985.
In an interview in 2011, O'Neill said: "Surfing for me was a very important part of my life. I'd work downtown in San Francisco and I'd get all screwed-up, and I'd go out and I'd jump in the ocean and everything would be alright again.
"All I wanted to do was surf, and when I opened that shop in my garage, I thought I would have a few guys there to sell suits and have guys to surf with.
"One of the guys up there told me: 'O'Neill, you are going to sell the five guys on the beach and you are going to be out of business'.
"Nobody is more surprised than I am about how this business has grown," O'Neill said.
He also said that his proudest achievement was the Sea Odyssey programme, which introduced schoolchildren to marine conservation.