Madagascar has a small Jewish population, but the island has not historically been a significant center for Jewish settlement. Nevertheless, an enduring origin myth across numerous Malagasy ethnic groups suggests that the island's inhabitants descended from ancient Jews, and thus that the modern Malagasy and Jewish peoples share a racial affinity. This belief, termed the "Malagasy secret", is so widespread that some Malagasy refer to the island's people as the Diaspora Jiosy Gasy (Malagasy Jewish Diaspora). As a result, Jewish symbols, paraphernalia, and teachings have been integrated into the religious practices of certain Malagasy communities. The island's small rabbinic Jewish population is outnumbered by numerous mystical groups identifying as Jewish or Israelite and practicing syncretic combinations of Christianity, Judaism, Islam, and traditional ancestor worship and animism. These include the roughly 2,000 members of the "approximate[ly]... dozens" of Messianic Jewish congregations in Madagascar, which incorporate Judaic elements into Christian belief.

Similar notions of Madagascar's supposed Israelite roots persisted in European accounts of the island until the early 20th century, and may have influenced a Nazi plan to relocate Europe's Jews to Madagascar.

Madagascar's small Jewish community faced challenges during the Vichy regime, which implemented antisemitic laws affecting the few Jews on the island. In the 21st century, some indigenous Malagasy communities informally identified with Jews and Judaism have adopted rabbinic Judaism, studying the Torah and Talmud across three small congregations and undergoing Orthodox conversion in the 2010s. The unified rabbinic Jewish community situated near Antananarivo practices a Sephardic liturgy and refers to its ethnic division within Judaism as Madagascar Sepharad.

There is a widespread, centuries-old belief in Madagascar that Malagasy people are descended from Jews, with "probably millions" of people in Madagascar claiming genealogical origins in ancient Israel. This belief is termed the "Malagasy secret", and is so common that some Malagasy refer to their people(s) as the Diaspora Jiosy Gasy (Malagasy Jewish Diaspora). The origin myths, which vary across clans, often include ancestors arriving at the shores of Madagascar wearing white and bearing "red zebu", a localized adaptation of the biblical red heifer tradition. Katherine Quanbeck records an oral testimony from a man of the Tavaratra clan, from Sandravinany, of his people's ancestors who...

...came from somewhere in the area of Medina, or somewhere on the sea coast of Saudi Arabia, in scores of botries [boats] full of families to the northern coast of Madagascar. Some of them, the Tantakara, stayed in the area of that northern coast, others continued southward along the eastern coast of Madagascar. The dhow of our family contained one red zebu and when the dhow reached the Vohipeno area, the zebu brayed, so they stopped here temporarily. But then they continued southward, past what is known as Fort Dauphin, and continued on around the southern coast, even going as far as Androka. At the mouth of that river, the zebu brayed again, two times; so they stopped there but eventually left again, and returned the way they had come. After travelling back eastward along Madagascar's southern coast, then northward along part of the eastern coast, at the Vohipeno area, the red zebu brayed three times. So they stopped there, and our family eventually moved as far south as Sandravinany, a region which was open totally, with no persons having settled it. We were the original Malagasy people in that area around what is now known as Sandravinany.

Further belief holds that Madagascar has been settled by Jews since ancient times, and that the island was associated with ancient Ophir. These same legends assert that the rosewood used in the construction of the Temple of Solomon came from the lowland forests of Madagascar.

Descent from members of this Solomonic fleet is prominently claimed by the Merina and Betsileo peoples. Betsileo legend associated with a site called Ivolamena describes two Betsileo ancestors, Antos and Cathy, sent by Solomon to Madagascar to look for gold and precious stones.

The Merina royal line has often claimed to descend from an ancient wave of Israelite migration that arrived via Asia in Madagascar, after being exiled by the Neo-Babylonian emperor Nebuchadnezzar. Antemoro people claim Moses as their forebearer. Sakalava and Antandroy people explain certain taboos within their respective cultures as originating with ancient Israelite ancestors. Some Malagasy theories of Jewish provenance suggest ancestral origin in one or more of the Ten Lost Tribes of Israel, most commonly Gad, Issachar, Dan, and Asher. Another narrative linking ancient Hebrews to Madagascar asserts that Madagascar was the site of the Garden of Eden (with various island rivers around the Malagasy settlement of Mananzara cited as the true Biblical Pishon), and that Noah's Ark departed from Madagascar at the time of the flood. One Antemoro legend recounts that the Islamic prophet Mahomet had five sons who all became kings in Arabia: Abraham, Noah, Joseph, Moses, and Jesus, the last four of them having fathered Tsimeto, Kazimambo, Anakara, and Raminia.