Oliva, known as The Myth due to his unbelievable physique, passed away at the age of 71 after suffering from kidney disease, according to German website Bodybuilding-magazin.de.
The Cuban star rose to fame in the 1960s, taking second place in the 1962 National Weightlifting Championship. He moved to the U.S. in 1963 after claiming political asylum to escape Fidel Castro's Communist regime, and continued to train after settling in Chicago, Illinois.
He went on to win the International Federation of BodyBuilders (IFBB) Mr. World and Mr. Universe titles, and was declared the undisputed world champion in 1967 when he was named Mr. Olympia.
Oliva faced competition from a young Schwarzenegger in 1969, but he managed to defeat the Austrian and retained the Mr. Olympia title for another year.
Schwarzenegger never lost a bodybuilding competition ever again and now the Hollywood action man has remembered his pal and former rival in a touching Twitter.com tribute.
In a blog post on Tuesday (13Nov12), the former Mr. Universe writes, ""Sergio Oliva was one of the greatest bodybuilders of all time & a true friend. A fierce competitor w/ (with) a big personality - one of a kind.""