Toku Nishio was a Japanese actor and voice actor born Yasunori Nishio on September 12, 1939, in Gifu Prefecture. He began his career in 1959 and was active until his death on July 19, 2005, in Tokyo. Throughout his career, he was represented by the Tokyo Actor's Consumer's Cooperative Society.

Nishio built a substantial body of work across anime, original video animations, theatrical films, video games, and tokusatsu live-action series. In anime, he is known for several prominent roles. He voiced Musashi Tomoe in the 1974 series Getter Robo and its subsequent theatrical features. He was the original voice of Mr. Popo in the Dragon Ball franchise, starting from the original Dragon Ball series in 1988 and continuing through Dragon Ball Z and Dragon Ball GT. He also portrayed South Kaiō in the Dragon Ball Z series and films. Another early significant role was Kanichi Mammoth Nishi in the 1970 series Ashita no Joe.

Nishio's career included many other anime roles across several decades. He voiced Seiji in the 1983 series Stop!! Hibari-kun!. In the 1974 anime Vicky the Viking, he played the role of Faxe. He was the voice of Babyface in the 1983 series Akū Daisakusen Srungle. He portrayed Zhu Bajie, known as Cho Hakkai, in the 1989 special Tezuka Osamu Story: I Am Son-Goku. His role as Zilkon was in the 1984 series Chikyū Monogatari Telepath 2500. In the 1986 film Gegege no Kitarō: Yōkai Daisensō, he voiced Frankenstein's Monster. Later in his career, he provided the voice for Conrad in the 1997 anime Berserk. His other anime credits include roles in The Irresponsible Captain Tylor, City Hunter, Lupin the Third Part II, and Nintama Rantarō, among many others.

Beyond anime, Nishio was a prolific voice actor in the tokusatsu genre, particularly for the Super Sentai series. He provided voices for numerous monster characters in shows such as Himitsu Sentai Goranger, Dai Sentai Goggle-V, Kagaku Sentai Dynaman, and Kyōryū Sentai Zyuranger. He also had voice roles in Kamen Rider Black and Kamen Rider Black RX.

Throughout his long career, Nishio frequently collaborated with many fellow voice actors, including regulars in the Dragon Ball and Super Sentai franchises, such as野泽雅子, 八奈见乘児, and 郷里大輔.