Since CrossFit’s founding in 2000, journalists, academics, and onlookers have noted the functional fitness brand’s ability to forge tight-knit communities of zealous exercisers. CrossFitters have likewise reflected upon how disciplining their bodies in community can connect them to a deeper sense of fulfillment and purpose. The cumulative effect of these observations has been to compare CrossFit to one of humanity’s most ubiquitous structuring phenomena: religion. This chapter examines religion in and around CrossFit. It introduces readers to the little-known story of two Harvard Divinity School graduate students who invited Greg Glassman to speak at Harvard Divinity School about the physical, social, and spiritual power of CrossFit. This event helped plant a seed in both the public imagination and CrossFit Inc.’s own self-understanding of CrossFit as a “spiritual-but-not-religious” community. Drawing upon interviews with Harvard Divinity School students, CrossFit executives, archived video footage, articles from The CrossFit Journal, and oral histories from gym owners, this chapter analyzes the religion of CrossFit. It outlines CrossFit Inc.’s reaction to being labeled a religion and CrossFit Inc.’s embrace of Harvard Divinity School, and it shows how CrossFit’s frequent comparison to religion reflects a back-and-forth relationship between analysts of religion and those whom they analyze. In so doing, this chapter offers a broader reflection on the categories we use to observe a social phenomenon like CrossFit, while detailing a particular history of CrossFit as a spiritual-but-not-religious community.