Ritual purity was a major goal of cultic activities in the Mediterranean world, but in a number of contexts, purity was also considered a desirable condition regardless of culticparticipation. This chapter discusses the concept of purity and purification from phenomenological,linguistic, and ritual perspectives. Attention is given to the variegated use of purity terminology and to the use of cognitive metaphor and conceptual blending theories to understand and explain the broad and common usage of purity-related language in various domains. The chapter surveys and analyses a limited selection of purification rites from Egypt, Mesopotamia, Persia, Israel, Greece, and Rome. This is done both with a view to historical development, influence, and interaction, and with the help of theorizing on ritual efficacy and social effects of purity codes. Particular attention is given to purifications with water, especially in Second Temple Judaism, as these are crucial to the further development of water rites in emerging Christianity.