Mikveh or mikvah (, () mikva'ot, mikvoth, mikvot, or (Yiddish) mikves, lit., "a collection") is a bath used for the purpose of ritual immersion in Judaism to achieve ritual purity.
Most forms of ritual impurity can be purified through immersion in any natural collection of water. However, some impurities, such as a zav, require "living water", such as springs or groundwater wells. Living water has the further advantage of being able to purify even while flowing, as opposed to rainwater which must be stationary to purify. The mikveh is designed to simplify this requirement, by providing a bathing facility that remains in contact with a natural source of water.
In Orthodox Judaism, these regulations are steadfastly adhered to; consequently, the mikveh is central to an Orthodox Jewish community. Conservative Judaism also formally holds to the regulations. The existence of a mikveh is considered so important that a Jewish community is required to construct a mikveh even before building a synagogue, and must go to the extreme of selling Torah scrolls, or even a synagogue if necessary, to provide funding for its construction.
Formed from the Semitic root ק-ו-ה (q-w-h, "collect"). In the Hebrew Bible, the word is employed in the sense of "collection", including in the phrase מקוה המים (miqwêh hammayim, "collection of water") in Gen. 1:10, Ex. 7:19, and Lev. 11:36. Ben Sira is the earliest author to use מקוה as a word for "pool" (Ecclus 43:20, 48:17) and the Mishnah is the earliest text to use it in the sense of "ritual bath".
Before the beginning of the first century BC, neither written sources nor archaeology gives any indication about the existence of specific installations used for ritual cleansing. Mikvoth appear at the beginning of the first century BC, and from then on, ancient mikvoth can be found throughout the land of Israel, as well as in historic communities of the Jewish diaspora.
In October 2020, a 2,000-year-old mikveh was found near Hannaton in northern Israel.