Hiroshi Kōsaka is a Japanese voice actor born on March 8 in Tokyo, Japan. He is affiliated with the talent agency Aksent. As a child, he dreamed of becoming a baseball player, but after being influenced by the anime series Saint Seiya and Gundam, he instead pursued a career in voice acting.

Kōsaka is perhaps best known for his role as Koduck, the Psyduck, in the 2023 stop-motion series Pokémon Concierge. His other notable anime roles include Iwashimizu, an informant, in the historical fantasy series My Happy Marriage in 2023, and Kyoukei Fukita in the film Psycho-Pass SS: Case. 2 - First Guardian. He also provided the voice for a police officer in the series Viral Hit. His name is sometimes written as Hiroshi Kousaka or with the Japanese characters 高坂 宙.