Hideo Yokoyama is a Japanese novelist who specializes in mystery novels. He is also known for his career as a journalist for the Jomo Shimbun, the regional paper in Gunma. He repeated his Kono Mystery ga Sugoi! No. 1 ranking in 2013 with Six Four (64). The English edition of Six Four, translated by Jonathan Lloyd-Davies, was shortlisted for the 2016 CWA International Dagger.