Nils Nelleßen is a German actor and voice artist, born in Oldenburg in 1971. He completed his acting training at the Hochschule für Film und Fernsehen Konrad Wolf in Potsdam-Babelsberg from 1994 to 1998. Early in his career, he gained recognition in theater, performing at venues such as the Hans-Otto-Theater in Potsdam and the Deutsches Theater in Berlin, and in 1997 he received a promotion award for young acting students. His on-screen career includes numerous film and television roles, with his most prominent live-action part being the recurring character of forensic pathologist Dr. Hildebrandt in the ZDF crime series Der Kriminalist, a role he played from 2006 to 2020.

Parallel to his on-screen work, Nelleßen has built a substantial career as a voice artist. He has been active as a voice actor for over fifteen years, lending his voice to characters in film and television. In the realm of anime and animation, he is known for providing the German voice for the character Enrico Pucci in the 2021 season of the anime series JoJo's Bizarre Adventure: Stone Ocean. His voice work also includes the role of Cubot in the animated series Sonic Prime from 2022 to 2024. Beyond animation, his voice acting portfolio encompasses the German dubbing of live-action roles, such as Alex in the Netflix series Who Killed Sara?.

In addition to his work in synchronization, Nelleßen is an established audiobook narrator, having voiced over sixty audiobooks. His voice is also heard as the station voice for the radio broadcaster NDR 1 Niedersachsen. He resides in Berlin and is a member of the Federal Association of Actors (BFFS).