Art As Witness is an invitation for professors, researchers, clergy, educators, students, and activists to creatively integrate the arts in theology and religious studies for a practical theology of arts-based research that prioritizes public witness. This methodology challenges the traditional written word as being the privileged norm, arguing that this emerging research genre is an excellent, viable, and necessary option for research that supports, promotes, and publicizes liberating theology for the marginalized, victimized, and oppressed. It includes a detailed case study of "Art Inside Karnes," the all-volunteer arts-based ministry of presence the author facilitated inside a for-profit immigrant family detention center that became the Power of Hope traveling art exhibit for education, advocacy, and public witness. This primer covers practical ethical, legal, and political matters; includes pedagogical examples for how to use arts-based research for student assessment in theology and religious studies; and provides an overview of arts options, including literary genres, visual arts, fabric arts, theater, filmmaking, and new media with digital content. Art as Witness features 40 illustrations, several case studies, and multiple contributing theologian-artists who engage the arts in themes that include immigration, HIV/AIDS, biblical studies, political protest, gender equity, gun law reform, racial justice, and more.