Conversion to Judaism is the process by which non-Jews adopt the Jewish religion and become members of the Jewish ethnoreligious community. It thus resembles both conversion to other religions and naturalization. The procedure and requirements for conversion depend on the sponsoring denomination. Furthermore, a conversion done in accordance with one Jewish denomination is not a guarantee of recognition by another denomination. Normally, though not always, the conversions performed by more stringent denominations are recognized by less stringent ones, but not the other way around. A formal conversion is also sometimes undertaken by individuals whose Jewish ancestry is questioned or uncertain, even if they were raised Jewish, but may not actually be considered Jews according to traditional Jewish law.

Ger toshav is a halakhic term used in Judaism to designate the legal status of a Gentile (non-Jew) living in the Land of Israel who does not want to convert to Judaism but agrees to observe the Seven Laws of Noah, a set of imperatives which, according to the Talmud, were given by God as a binding set of universal moral laws for the "sons of Noah"—that is, all of humanity. A ger toshav, especially one who decides to follow the Noahic covenant out of religious belief rather than ethical reasoning, is commonly deemed a "Righteous Gentile", and is assured of a place in the World to Come .