Lesslie Newbigin was arguably the greatest missionary thinker of the twentieth century. After a successful missionary career in south India, Newbigin pioneered missionary engagement with the secular West and resurgent Islam. He also led the way in arguing that the Church's mission can only be understood in light of the doctrine of the Trinity. Over fifty years ago, Newbigin called for the further development of missionary thinking grounded in the Triune being of God. This work is in response to that call. Adam Dodds provides the first in-depth study of Newbigin's trinitarian theology of mission. Dodds constructs a systematic account of the central features of the mission of the Triune God: the Triune being of God, the mission of the Son, the mission of the Holy Spirit, and the mission of the church. This book contributes to our understanding of the work of Lesslie Newbigin, offers a systematic theological account of the mission of the Triune God, and contributes to the retrieval of Christian mission from the theological margins back to a place of central importance to Christian theology.