A mikveh (Hebrew: מִקְוָה "gathering" [of water]) or mikvah is a bathing pool in which a person immerses themself as part of the cleansing process (tevilah "immersion") to ritual purity in Judaism and Messianic Judaism. Natural bodies of moving water such as oceans and rivers, rainwater-replenished wells and spring-fed lakes are also considered to be mikvehs. However, problems of accessibility, weather and lack of privacy have led to the construction of man-made pools.
Many Jewish women undergo ritual cleansing on a monthly basis, following menstruation, and also just before marriage and just after childbirth. Grooms immerse themselves on their wedding day, and some men also immerse themselves in a mikveh before the Sabbath and the festivals, particularly just before Yom Kippur. Tevilah is also one of the requirements at the end of the process of conversion to Judaism and some schools of Messianic Judaism.
Participants first remove all clothing and even jewellry to ensure that the entire body is washed by the waters, and then bathe or shower in a separate area before immersing the body entirely in the mikveh: Jewish halachah stipulates that a person must be externally scrupulously clean before the ritual cleansing. "The function of mikvah is not to enhance physical hygiene. The concept of mikvah is rooted in spiritual [hygiene]." The mikveh pool itself must be built into the ground and bathtubs or similar receptacles are therefore unsuitable. The mikveh must contain a minimum of two hundred gallons of rainwater, gathered in accordance with an intricate set of Jewish laws.