Donald Allen Crosby (born 7 April 1932) is an American theologian who is Professor Emeritus of Philosophy at Colorado State University, since January 2000. Crosby's interests focus on metaphysics, American pragmatism, philosophy of nature, existentialism, and philosophy of religion. He is a member of the Highlands Institute of American Religious and Philosophical Thought (HAIRPT) and has been a leader in the discussions on Religious Naturalism.