Kosuke Koyama was a Japanese, Protestant Christian theologian. Koyama was born in Tokyo in 1929, of Christian parents; 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, 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.