The prominence of religious groups, religious motifs, and religious and theological claims in the anti-trafficking movement is useful for exploring how social movements are shaped by religious actors and claims and, in turn, use religion in the process of creating social change. The anti-trafficking movement can be situated in relation to three key previous social movements: the 18th–19th-century abolition movement that sought to abolish chattel slavery, the 19th–20th-century anti-white slavery campaigns of the social purity movement that sought to eliminate prostitution, and the late 20th-century movement that sought to address Christian persecution through promoting religious freedom. By highlighting the way that the anti-trafficking movement draws on and extends the moral claim-making of each of these social movements, these earlier movements are revealed as shaping the social movement ecology out of which the contemporary anti-trafficking movement emerges and in which it functions. Further, exploring the movement to end human trafficking in relation to these social movements suggests at least three significant ways religion matters in social movements: as a source of moral legitimacy, as a source of moral clarity, and as a cultural resource. As a source of moral authority, religion provides a source of grounding that lends credibility to movements’ moral claims by situating them in something larger than immediate interests and experiences. As a source of moral clarity, religion is a source of the moral values that animates social movements and sustains them through challenges. As a cultural resource, religious sensibilities influence how social movements perceive issues and formulate responses to them.