Oreal Donald Perras (August 25, 1942 – February 18, 2017) was a Canadian professional wrestler, better known by the ring name "The Russian Bear" Ivan Koloff, under which name he was billed as being from Russia and, following the dissolution of the Soviet Union, Ukraine. He was the third wrestler to hold the WWWF Championship. In April 2025, Koloff was inducted into the WWE Hall of Fame.

Perras was born in Montreal, Canada and raised on a dairy farm in rural Ontario along with his six brothers and three sisters.

Since first watching professional wrestling on TV at the age of eight, he wanted to become a wrestler, and would often wrestle with his brothers growing up. At age 18, he left high school and joined Jack Wentworth's wrestling school in Hamilton, Ontario, where he would lift weights and learn wrestling holds.

Perras debuted as an Irish rogue villain character named Red McNulty, billed from Dublin, Ireland, and wrestling with an eyepatch. For the next three years, he wrestled around the Toronto area, eventually quitting his regular job to wrestle in the north-western area of Canada. There, Perras acquired much wrestling experience, and from there he made his first trip to Japan.

In 1967, Perras became "The Russian Bear" Ivan Koloff, a bearded villainous character billed from Ukraine (the name was taken from Dan Kolov, an actual Bulgarian wrestler who had competed in Canada in the 1930s), and debuted with the International Wrestling Association in Montreal. He defeated Johnny Rougeau for the IWA International Heavyweight Championship the following year. Koloff debuted in the World Wide Wrestling Federation in late 1969, managed by "Captain" Lou Albano. He soon started a rivalry with then-WWWF World Heavyweight Champion Bruno Sammartino. On January 18, 1971, Koloff defeated Sammartino in Madison Square Garden for the WWWF World Heavyweight Championship by pinfall after a knee drop from the top rope, ending Sammartino's seven and two-thirds years reign. Koloff lost the championship 21 days later to Pedro Morales, essentially being used as a "transitional champion" to move the title from Sammartino to Morales without the two fan favorites working against each other, much like Stan Stasiak and The Iron Sheik would be in later years. After the loss, Koloff remained a contender for the title but never reclaimed it, leaving the WWWF in 1971. During his time in the WWWF, Koloff weighing in at 310 pounds (140 kg) wrestled WWWF World Heavyweight Championship title matches against Sammartino, Morales, Superstar Billy Graham and Bob Backlund, holding the distinction, with fellow villain Stan Stasiak, as one of only two men to challenge all four of these champions. Koloff would also challenge Sammartino for the WWWF World Heavyweight Championship in the first ever steel cage match at Madison Square Garden in a rematch loss on December 15, 1975. He fought in the WWWF from 1975 to 1976, 1978–1979 and 1983.

During the 1970s and 1980s, Koloff found success in the National Wrestling Alliance, winning many regional tag team and singles titles in the Georgia, Florida, and Mid-Atlantic territories. In February 1981, he teamed with Ray Stevens to defeat Paul Jones and Masked Superstar to capture the NWA World Tag Team Championship. This would be the first of his four reigns as NWA World Tag Team Champion, later winning the belts with Don Kernodle and twice with Russian sympathizer, Krusher Kruschev, and his "nephew" (kayfabe), Nikita Koloff as The Russian Team using the "Freebird Rule".

In April and May 1973, Koloff wrestled in Japan for the International Wrestling Enterprise promotion as part of its Dynamite Series. In his debut match, he teamed with Mad Dog Vachon to defeat Great Kusatsu and Strong Kobayashi for the IWA World Tag Team Championship in a two-out-of-three falls match. They lost the titles to Great Kusatsu and Rusher Kimura several weeks later.

The Russians (which also included Krusher Kruschev) were a top villainous group from 1984 to 1986, and Nikita, under Perras' training and mentoring, and by association, became a hated villain in his own right, and would go on to have a successful singles career of his own. After Nikita turned on Ivan to join their enemy Dusty Rhodes in 1986, the latter teamed with Vladimir Petrov and Dick Murdoch to get revenge. Koloff's biggest NWA feuds were against Rhodes, The Road Warriors, The Rock 'n' Roll Express (Ricky Morton and Robert Gibson) and Magnum T. A. In 1988, Koloff spent time in Paul Jones' faction, The Paul Jones Army, where he was a "coach" of sorts for The Powers of Pain, The Barbarian and The Warlord. He later split with Jones, reunited with Nikita, and feuded with Jones' team, The Russian Assassins, before leaving Jim Crockett Promotions in January 1989. In 1992, Koloff also wrestled in the first television main event of Jim Cornette's Smoky Mountain Wrestling, beating Bobby Fulton. He lost to Ron Garvin at Tim Horner's National Championship Wrestling on July 22, 1994. He retired afterwards.