Hideo Yokoyama (横山 秀夫, Yokoyama Hideo, born 1957) is a Japanese novelist. Yokoyama specializes in mystery novels. 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.He is known for his career as journalist for the Jomo Shimbun, the regional paper in Gunma.