Karaism is the longest surviving form of sectarian Judaism, but its origins remain a mystery. Its opponents, the Rabbanites, attribute its founding to the eighth-century Anan ben David, a disappointed candidate to be exilarch (head of the Babylonian captivity), whose pique and anger caused him to secede from normative Judaism. Karaites counter that their form of Judaism is the original one and that the schism between the two groups of Jews dates from the Second Temple period, when the Rabbanite concept of the Oral Torah was invented. Modern research has demonstrated that Anan was most certainly not the founder of Karaism (his followers were known as Ananites; they eventually coalesced with the group known as Karaites, who then retroactively adopted Anan as one of their patres ecclesiae); opinion remains divided as to how much connection, if any, there is to Second Temple groups or whether Karaism is purely a medieval movement. Whatever their origins, by the tenth century the Karaites were a well-organized alternative to Rabbinic Judaism and created parallel institutions that developed their own brand of law, exegesis, linguistic studies, polemics, and historiography.

Karaite history, going back to the formative “Golden Age” in the ninth to eleventh centuries in the Land of Israel, has been marked by growing rapprochement with the dominant Rabbanites. Generally Karaites were accepted as part and parcel of the larger Jewish communities, but intermarriage between the groups was frowned on or forbidden. Although Karaites maintained their own institutions and religious practices, they turned more and more to Rabbanite texts and teachers. Only in Czarist Russia, where a Jewish identity involved major disabilities, did Karaites disassociate themselves from the rest of the Jewish community; in Islamic countries, however, there was never such a break. At the start of the twentieth century the largest communities were found in Egypt, Crimea, and Lithuania. Today Karaites, most of whom are of Egyptian origin, live mainly in Israel as a marginal Jewish group.