Societies are marked by rituals, performative acts that are explicit and implicit, formal and informal. This chapter argues that rituals create and mark social reality in four principal ways. First, by creating a social reality, rituals establish or reinforce expectations, relationships, and roles; they create a web of social bonds. Second, by inviting participation in a social reality, rituals maintain social stability and harmony; they create sustaining social structures. Third, rituals by placing individuals within a social reality enable individuals to understand themselves as part of specific groups invested in particular activities, commitments, and traditions; rituals by creating social reality allow individuals to understand their position within the social geography of the world. Fourth, rituals by placing humans within a social reality disclose the significance and meaning of time, including the passages of human life, from reproduction, birth, marriage, and suffering to death. Rituals declare social boundaries.