Susumu Chiba is a Japanese voice actor born on September 13, 1970, in Kanagawa Prefecture, Japan. He is affiliated with the talent management firm Office Osawa. Chiba began his career in the entertainment industry after developing an interest in acting during his college years, initially participating in theater workshops for enjoyment before gaining a professional awareness of voice acting upon joining Office Osawa, an agency known for handling a significant amount of narration work. His early professional jobs included narrating commercials. He made his debut as an anime voice actor in 1996.

Chiba's career is marked by a wide array of roles across various anime series, demonstrating his range as a performer. A pivotal and deeply memorable role for him was that of Fujiwara no Sai in the acclaimed anime Hikaru no Go (2001-2003). He has described the experience of playing this ethereal character as one that left the deepest impression on him.

He is also widely recognized for his long-standing portrayal of the sincere and powerful Isao Kondō, the commander of the Shinsengumi, throughout the entirety of the Gintama franchise. This includes the original Gintama series, Gintama', Gintama°, the film Gintama: The Final, and the compilation film Gintama on Theater 2D: Shinsengumi Crisis Arc. His other notable roles from the 2000s include Seiji Hayami in Cutie Honey Flash, Chiaki Nagoya in Phantom Thief Jeanne, Kidōmaru in Naruto, Shō Sai in The Story of Saiunkoku, Takuma Ichijō in Vampire Knight, and Welkin Gunther in Valkyria Chronicles.

In addition to these prominent parts, Chiba has consistently contributed to a broad spectrum of series, taking on roles such as Eld Gin in both Attack on Titan and its spin-off Attack on Titan: Junior High, and Raymond McGuire in Phantom ~Requiem for the Phantom~. He has also voiced characters in the Pretty Rhythm franchise, the Transformers franchise, and in the film A Whisker Away. His more recent work includes the role of Otoharu Takanashi in the IDOLiSH7 series and Mirage in Fire Force. For certain roles in adult-oriented games and animations, he is credited under the alias "Progress". His career, which began in 1996, has continued actively into the 2020s, with roles in new projects and reprisals of long-standing characters.