Born in Glasgow, Montana in 1926, Reeves moved to California at age 10 with his mother Goldie Reeves after his father Lester Dell Reeves died in a farming accident. Reeves developed an interest in bodybuilding at Castlemont High School and trained at Ed Yarick's gym in Oakland, California. After graduating from high school, he enlisted in the United States Army during World War II, and served in the Philippines.

After his military Service and winning the 1947 AAU Mr. America, Reeves became interested in pursuing an acting career. He studied acting under Stella Adler, but after arguments he was refunded his tuition. In 1948 he was selected by Cecil B. DeMille for the lead role in DeMille's Samson and Delilah, for which he received extensive training. In order to look convincing on-camera, he was told to lose 15 pounds; he subsequently turned the movie offer down because he could not compete in bodybuilding at the diminished weight.

In 1949 he filmed a Tarzan-type television pilot called Kimbar of the Jungle, and in 1950 became Mr. Universe. In 1954 he had a small role in his first major motion picture, the musical Athena, playing the boyfriend of Jane Powell's character. That same year, Reeves had a small supporting role as a cop in the Ed Wood film Jail Bait. These two films are the only ones Reeves made in the United States where his actual voice was used; Reeves acted in Italian-made films for the remainder of his career, where all dialogue and sound effects were added in post-production.

Reeves guest-starred on The George Burns and Gracie Allen Show as the owner of a gym. On December 17, 1954, Reeves guest-starred in the ABC sitcom Where's Raymond?, starring Ray Bolger as Raymond Wallace, a song-and-dance man. Reeves played a well-built office employee whom Wallace sees in the company of Wallace's girlfriend, Susan.

In 1957, Reeves went to Italy and played the lead character in Pietro Francisci's Hercules, a relatively low-budget epic based loosely on the tales of Jason and the Argonauts, though inserting Hercules into the lead role. The film was a major box-office success, grossing $5m in the United States in 1959. Its commercial success led to a 1959 sequel Hercules Unchained, with Reeves reprising his role.

From 1959 through 1964, Reeves went on to appear in a string of sword and sandal movies shot on relatively small budgets and, although he is best known for his portrayal of Hercules, he played the character only twice: in the 1957 film (released in the USA in 1959) and its 1959 sequel Hercules Unchained (released in the US in 1960). By 1960, Reeves was ranked as the number-one box-office draw in twenty-five countries around the world. He played a number of other characters on-screen, including Sir Edward Bulwer-Lytton's Glaucus of Pompeii; Goliath, the bane of the barbarians (actually called "Emiliano" in the Italian version); Avar hero Hadji Murad; Romulus, the legendary founder of Rome (opposite Gordon Scott as his twin brother Remus); Pheidippides, the famous wartime messenger of the Battle of Marathon; pirate and self-proclaimed governor of Jamaica, Captain Henry Morgan; Randus, the son of Spartacus; and Karim, the fabled Thief of Baghdad. Twice he played Aeneas of Troy and twice he played Emilio Salgari's Malaysian hero, Sandokan.

Reeves turned down the James Bond role in Dr. No (1962) because of the low salary the producers offered. Reeves also turned down the role that finally went to Clint Eastwood in A Fistful of Dollars (1964) because he did not believe that "Italians could make a western".

In 1968 Reeves appeared in his final film, a spaghetti Western he co-wrote, titled I Live For Your Death! (later released as A Long Ride From Hell). His last screen appearance was in 2000 when he appeared as himself in the made-for-television A&E Biography: Arnold Schwarzenegger – Flex Appeal.

In the 1973 British musical stage production The Rocky Horror Show, and its 1975 film counterpart The Rocky Horror Picture Show, Dr. Frank N. Furter introduces himself to Brad and Janet with the song Sweet Transvestite. The lyrics include, "Or if you want something visual / That's not too absymal / We can take in an old Steve Reeves movie".

Later in his life, Reeves bred horses and promoted drug-free bodybuilding. The last two decades of his life were spent in Valley Center, California. He bought a ranch with savings from his film career and lived there with his second wife, Aline, until her death in 1989.

Authorized Biographer Chris LeClaire lived and worked for Steve Reeves at his Valley Center, California horse ranch during the summers of 1993 and 1994 while writing and researching material for his book Worlds To Conquer, The Auhorized Biography Of Steve Reeves ISBN no. 09676775413, published First Edition December 1999, Second Edition 2017. LeClaire conducted taped interviews with Reeves up until the actor's death in Spring 2000. Worlds To Conquer is published in both standard book bound format, as well as electronic eBook Kindle version.

In 1994, Reeves and Business partner George Helmer started the Steve Reeves International Society; in 1996, it incorporated to become Steve Reeves International, Inc.

On May 1, 2000, Reeves died from a blood clot after having had surgery two days earlier. He died at Palomar Hospital in Escondido, California, where his second wife had also died.

Freelance Writer Rod Labbe interviewed Reeves, and the article appeared in Films of the Golden Age magazine, summer 2011. It was conducted in 1997 and was the last extensive interview Steve Reeves did.