Kōji Hirayama (平山 幸司, Hirayama Kōji, born November 9, 1969) is a Japanese politician of the Democratic Party of Japan, a member of the House of Councillors in the Diet (national legislature). A native of Goshogawara, Aomori and graduate of Kanto Gakuin University and Keio University, he was elected for the first time in 2007.