Few missiologists have impacted mission theory and practice among Churches of Christ as significantly as has Dr. Gailyn Van Rheenen, yet his global missiological influence has extended far beyond the boundaries of his denominational heritage. This Festschrift, in honor of Gailyn Van Rheenen, contains original missiological contributions from colleagues and former students. Most chapters were presentations at the inaugural Gailyn Van Rheenen Sessions in Mission and World Christianity at the 2021 Christian Scholars'' Conference in Nashville, Tennessee. The volume is organized to parallel the phases of Van Rheenen''s career--Africa, academic missiology, and Mission Alive, a North American church-planting organization. His legacy is one that wonderfully embodies critical theory and robust practice.