Thomas Kästner is a German actor and voice actor born in 1942. He completed his acting training and stage proficiency examination in Berlin in 1962. His career encompasses work as a theatre actor, cabaret performer, and extensive activity in dubbing and voice-over for film and television.

Since 1979, Kästner has also worked as a dialogue director for dubbing, contributing to animated series, feature films, and television series. He has amassed a significant number of voice roles, with over one thousand credited parts. One of his most notable long-term roles is providing the German voice for William B. Davis as the character Cigarette Smoking Man in the series The X-Files. He has also frequently dubbed actors such as Alan Dale and Gojko Mitić. In the realm of anime and animation, he voiced the character Hawkmon in the German dub of the 2020 film Digimon Adventure: Last Evolution Kizuna. His other voice work includes the role of The One in the animated film The Empire of Corpses and the character Kuiil in the series The Mandalorian. Beyond on-screen work, Kästner has also been active as a voice actor in numerous radio plays and audio productions.