Gen Nakajima was a Japanese actor and voice actor born on September 11, 1925, in Taitō, Tokyo. He began his career on stage with the theater companies Gekidan Bunkaza and Gekidan Izumiza. Nakajima was also a founding member of the talent agency Tokyo Actor's Consumer's Cooperative Society (known as Haikyō), where he was affiliated.

In voice acting, Nakajima is known for his role in the 1965 anime series Uchū Patrol Hopper (also known as Patrol Hopper: Uchūkko Jun). In this series, he provided the voice for the character Director Hock, sometimes referred to as Commander Hock. Beyond this anime role, his career was extensive in Japanese film and television, where he was frequently cast in the role of a driver. His live-action credits include appearances in the 1973 film Godzilla vs. Megalon as a dump truck driver, and guest roles in numerous television dramas and tokusatsu series such as Robot Detective, Taiyō ni Hoero!, and Hissatsu series. His career spanned from the 1960s through the 1980s.