Jeff Lumby, sometimes credited as Jefferson Lumby, is a Canadian actor and voice actor. Born in 1955 in Kitchener, Ontario, he has been active in the entertainment industry since 1983. While he is widely recognized for his live-action role as Winston Rothschild III on the long-running Canadian comedy series The Red Green Show, he has also built a significant career providing voices for animated series and anime dubs.

Lumby is known to fans of the Sailor Moon franchise for his work in the original English dub produced by Cloverway. He voiced the role of Professor Souichi Tomoe, the mad scientist and primary antagonist of the series third season, Sailor Moon S. In the same season, he also provided the voices for the villainous entities Germatoid and Master Pharaoh 90. His work in the franchise extends to the feature film Sailor Moon S: The Movie, where he played the character Kakeru Oozora. Additionally, he voiced the minor role of Misha in the original Sailor Moon series. His sister, Lisa Lumby-Richards, worked as a scriptwriter for the same English adaptation of Sailor Moon.

Beyond Sailor Moon, another significant anime voice role for Lumby is Junk in the series Kero Kero Keroppi no Christmas Eve no Okurimono, which is part of the larger Keroppi and Friends franchise. Junk is characterized as Keroppi's larger friend who has the ability to transform into a rock, appearing in various adventures across the series.

His voice acting portfolio includes a wide range of work across many animated productions. He voiced Charles La Puck, the money-grubbing studio executive on the Canadian version of the game show Skatoony. Other animated roles include Jason on The Little Flying Bears, the Raccoon on Peep and the Big Wide World, Leonard Sprocket on Ricky Sprocket: Showbiz Boy, Terry on Fugget About It, and the Narrator in the 2015 revival of George of the Jungle. He has also performed various characters on shows such as Odd Job Jack, Atomic Betty, Sons of Butcher, Wayside, and Wishfart.

In addition to acting, Jeff Lumby has worked extensively in radio. He spent eight years as a radio personality at the Hamilton, Ontario station CJXY-FM and later co-hosted the morning show on Toronto station CISS-FM. He subsequently worked as the lead morning host for CJDV-FM in the Kitchener-Waterloo region, as an interim host on sports radio station The FAN 590 in Toronto, and as part of the morning crew on 105.3 Kool FM.