Cleonir dos Santos was a Brazilian actor and voice actor, born on July 9, 1944, in Rio de Janeiro, Brazil. He began his artistic career at the age of seven as a radio actor and became known as a child prodigy at TV Tupi. His career spanned radio, theater, television, and film before he became one of the pioneers of dubbing in Brazil starting in the late 1950s.

He is widely recognized for his extensive work dubbing anime and animated series. His notable roles in this genre include the title character Príncipe Planeta in Prince Planet, Steve Armstrong in Voltes V, and Kenny Carter in Wonder Three. He also voiced Bob in the series King Kong - 00 1/7 Tom Thumb and was the original Portuguese voice of Speed Racer in the classic anime of the same name. His other anime credits include Anthony in Candy Candy, Joe in Groizer X, Sanshiro in Judo Boy, and Ryusuke Domon in Star Blazers: The Bolar Wars. He also lent his voice to Chip Chase in the Brazilian dub of The Transformers.

Beyond anime, dos Santos had a prolific career dubbing characters for Western animation and live-action productions. For a significant period, he was the most prominent voice of Mickey Mouse in Brazilian dubs, a role he held from the early 1970s into the 1990s. He also voiced other iconic characters such as Fred in Scooby-Doo, following his predecessor Luiz Manoel, and the Coelho Branco (White Rabbit) in Alice in Wonderland. His dubbing work extended to series like He-Man and the Masters of the Universe, where he voiced Abelhão, and The Adventures of Super Mario Bros. 3.

Dos Santos was known for the distinct voice he brought to his characters. In a 1995 interview, he recounted a memorable moment when the creator of the character Pimentinha, upon hearing his dubbing work in Brazil, sought him out personally to express that dos Santos's voice was exactly what he had imagined for the character. His passion for his work was evident, particularly for series like Speed Racer, which he made a point to watch even during the dubbing process.

In addition to his voice work, Cleonir dos Santos maintained an active career as an on-screen actor. In the late 1970s and 1980s, he appeared in several Brazilian telenovelas for TV Globo, including Maria, Maria (1978), A Sucessora (1978), and O Outro (1987), as well as the TV Manchete novela Dona Beija (1986). Cleonir dos Santos passed away on December 9, 1998, in Rio de Janeiro at the age of 54, due to internal hemorrhaging resulting from a car accident.