Bret Clifton Gilliam (born February 3, 1951) is a pioneering technical diver. He is most famous as the founder of the certification agency Technical Diving International, and as the one time holder of the world record for deep diving on air. He is also one of diving's most popular writers. Gilliam is the author or coauthor of 72 books, over 1500 feature magazine articles, and over 100 magazine cover photos. In his diving career he has logged over 19,000 dives since 1959.