Tsuyoshi Koyama is a Japanese voice actor and actor born on October 4, 1967, in Aichi Prefecture, Japan. He is a graduate of Waseda University and is affiliated with the talent agency Across Entertainment. While his career as an on-screen actor began in 1991, his voice acting debut came later in 1999 with a role in the television anime Turn A Gundam. He is married to the anime song singer Mikuni Shimokawa.

Koyama is known for his distinctive, husky bass voice, which frequently leads him to be cast in roles for middle-aged or older characters. Despite the often serious or intimidating nature of the characters suggested by his voice and appearance, he is also recognized for his versatility and expressive range, capable of handling both comedic and serious roles.

His career features a substantial number of voice roles in a wide variety of anime series. He has played Kurou in the Utawarerumono franchise, including Utawarerumono: Mask of Truth. He is the voice of Jyūbei in the Yashahime: Princess Half-Demon series and its second act. His other notable roles include Derick Ross in Double Decker! Doug & Kirill, Kenneth in If It’s for My Daughter, I’d Even Defeat a Demon Lord, and Vassago (also known as PoH) in the Sword Art Online: Alicelyn series. He also voices Gunther in Ascendance of a Bookworm, Tobio in Uchū Nanchara Kotetsu-kun, and has appeared in projects such as Lupin III: Goodbye Partner as Norman, Mai Mai Miracle as Tatara, and the Hunter X Hunter OVAs as Gensuru. His filmography further includes Boax in Princess Arete, Atsuhiko Agata in KADO: Beyond Information, Bazra Bearmors in Lost Song, Cyborg 005/Geronimo Jr. in Cyborg 009 Vs. Devilman, Kirin in Chikomaru, and Benwood in I Left My A-Rank Party.

In addition to his extensive anime work, Koyama is highly active in video game voice acting. He is well-known for his role as Bang Shishigami in the BlazBlue series. Other prominent game roles include Dickson in Xenoblade Chronicles, Goro Takemura in the Japanese dub of Cyberpunk 2077, and Admiral Galleus in Monster Hunter Rise: Sunbreak. He also has a notable history in tokusatsu, providing the voice for Kamen Rider Odin and various transformation devices in Kamen Rider Ryuki, as well as voices in Kamen Rider Den-O and Kamen Rider Ex-Aid.

Beyond acting, Koyama is also a singer and songwriter, having composed and performed character songs for some of his roles, most notably for the Utawarerumono franchise. He is also known to be an enthusiast of mahjong.