A diaspora (from Greek διασπορά, "scattering, dispersion") is "the movement, migration, or scattering of people away from an established or ancestral homeland" or "people dispersed by whatever cause to more than one location", or "people settled far from their ancestral homelands".

The word has come to refer to historical mass-dispersions of people with common roots, particularly movements of an involuntary nature, such as the expulsion of Jews from the Middle East, the African Trans-Atlantic slave trade, the southern Chinese during the coolie slave trade, or the century-long exile of the Messenians under Spartan rule.

Recently, scholarship has distinguished between different kinds of diaspora, based on its causes such as imperialism, trade or labor migrations, or by the kind of social coherence within the diaspora community and its ties to the ancestral lands. Some diaspora communities maintain strong political ties with their homeland. Other qualities that may be typical of many diasporas are thoughts of return, relationships with other communities in the diaspora, and lack of full assimilation into the host country.

The Jewish diaspora (or simply the Diaspora) is the English term used to describe the Galut גלות (Yiddish: 'Golus'), or 'exile', of the Jews from the region of the Kingdom of Judah and Roman Judaea and later emigration from wider Eretz Israel.

The diaspora began with the 6th century BCE conquest of the ancient Kingdom of Judah, the destruction of the First Temple (c. 586 BCE), and the expulsion of the population, as recorded in the Bible. The Babylonian ruler, Nebuchadnezzar allowed them to remain in a unified community in Babylon. Another group of Jews fled to Egypt, where they settled in the Nile delta. From 597 BCE onwards, there were three distinct groups of Hebrews: a group in Babylon and other parts of the Middle East, a group in Judaea, and another group in Egypt. While Cyrus the Persian allowed the Jews to return to their homeland in 538 BCE, most chose to remain in Babylon. A large number of Jews in Egypt became mercenaries in Upper Egypt on an island called the Elephantine. All of these Jews retained their religion, identity, and social customs; both under the Persians and the Greeks, they were allowed to conduct their lives according to their own laws.