Reconstructionist Judaism is a Jewish movement that views Judaism as a progressively evolving civilization rather than a religion, based on concepts developed by Mordecai Kaplan (1881–1983). The movement originated as a semi-organized stream within Conservative Judaism and developed from the late 1920s to 1940s, before it seceded in 1955 and established a rabbinical college in 1967. Reconstructionist Judaism is recognized by some scholars as one of the five streams of Judaism alongside Orthodox, Conservative, Reform, and Humanistic.

There is substantial theological diversity within the movement. Halakha (Jewish law) is not considered normative and binding, but is instead seen as the basis for the ongoing evolution of meaningful Jewish practice. In contrast with the Reform movement's stance during the time Kaplan was writing, he believed that "Jewish life [is] meaningless without Jewish law" and one of the planks he wrote for the proto-Reconstructionist Society for the Jewish Renaissance stated, "We accept the halakha, which is rooted in the Talmud, as the norm of Jewish life, availing ourselves, at the same time, of the method implicit therein to interpret and develop the body of Jewish Law in accordance with the actual conditions and spiritual needs of modern life." The movement also emphasizes positive views toward modernity, and has an approach to Jewish customs which aims toward communal decision-making through a process of education and distillation of values from traditional Jewish sources.

The movement's 2011 A Guide to Jewish Practice describes a Reconstructionist approach to Jewish practice as "post-halakhic" because the modern world is one in which Jewish law cannot be enforced. Obligation and spiritual discipline exist without the enforcement of a functioning legal system. Thus, Reconstructionist Jews take Jewish law seriously as a source and resource that can shape expectations while not necessarily seeing themselves as bound by inherited claims of obligation. Therefore, the practices advocated in the guide are not monolithic, and commentators provide further insights, arguments, and alternative approaches that span the broad range of views advocated by Reconstructionist rabbis and scholars. The guide states that it "assumes that thoughtful individuals and committed communities can handle diversity and will of necessity reach their own conclusions".