Hideo Yokoyama(横山 秀夫Yokoyama Hideo, born 1957) is a Japanese novelist. Yokoyama specialized in mystery novels. He worked constantly during the first three days of 2003 and received a heart attack and subsequent hospitalization on the fourth. His best-selling work was Doki. He is known for his career as journalist for the Jomo Shimbun, the regional paper in Gunma.