Kosuke Koyama (小山 晃佑 Koyama Kōsuke, December 10, 1929 – March 25, 2009) was a Japanese, Protestant Christian theologian.
Koyama was born in Tokyo in 1929, of Christian parents (Cohn-Sherbok, 1998). He later moved to New Jersey in the United States, where he completed his B.D. at Drew Theological Seminary and his Ph.D., on the interpretation of the Psalms of Martin Luther, at Princeton Theological Seminary, completing his Ph.D. in 1959.
After teaching at a theological seminary in Thailand, he was the executive director of Association of Theological Schools in Southeast Asia with his office in Singapore from 1968 to 1974, and the editor of Southeast Asia Journal of Theology, and the Dean of Southeast Asia Graduate School of Theology. After that he worked as Senior Lecturer in Religious Studies at the University of Otago in Dunedin in New Zealand, from 1974 to 1979. He later worked at the Union Theological Seminary in New York City, where he stayed until his retirement in 1996 as John D. Rockefeller Jr. Professor Emeritus of World Christianity. To his close friends and family, he was known as "Ko". Along with Kazoh Kitamori, he is considered one of the leading Japanese theologians of the twentieth century.
In works such as Water Buffalo Theology and Three Mile an Hour God, he defended a theology that he considered to be accessible to the peasantry in developing nations, rather than an overly academic systematic theology. In total, Koyama wrote thirteen books. One of his most well-known books, "Water Buffalo Theology", was described as "ecological theology, liberation theology and contribution to Christian-Buddhist dialogue". In No Handle on the Cross: An Asian Mediation on the Crucified Mind (1976), Koyama explained how the cross can be considered the symbol of Christian suffering, and began the book with a chapter entitled "The Cross and the Lunchbox". Koyama explained, in the preface to this book, which he wrote in Tokyo at Christmas 1975, how he did Christian missionary work in Thailand from 1960 to 1968, and how his experiences in Thailand rekindled interest in Asian religion in him (Koyama, 1976). He also explained in the preface how the book grew out of the Earl Lectures which he delivered at the Pacific School of Religion in California. Koyama also spoke at a conference in Edinburgh in 1985, in which he described God as "a hot God", suggesting a certain dynamic quality to the attributes of God.