Mukai Osamu is a Japanese actor. He graduated from Meiji University, and majored in genetic engineering. While he was attending university, he worked as a bartender. He became a full-time employee there after graduation, and he became a manager later. While working as a bartender, he got into the magazine Tokyo Graffiti. A reader later recruited him to be an actor. Mukai's first main role was in the 2006 Japanese television drama Nodame Cantabile.
He has been married to Ryôko Kuninaka since December 28, 2014.