Kōsaku, Kosaku or Kousaku (written: 功作, 宏作, 幸作, 耕作, 耕筰, 興作, 孝作 or 浩作) is a masculine Japanese given name. Notable people with the name include:
*, Japanese baseball player
*, Imperial Japanese Navy admiral
*, Japanese archaeologist and academic
*, Japanese footballer
*, Japanese karateka
*, Japanese sumo wrestler
*
Kosaku Shimada (born 1944), Japanese golfer
*, Japanese poet and writer
*, Japanese composer and conductor
*, Japanese physician and translator
*, Japanese mathematician
{{DEFAULTSORT:Kosaku
Japanese masculine given names