A diaspora (/daɪˈæspərə/ dy-ASP-ər-ə) is a population that is scattered across regions which are separate from its geographic place of origin. The word is used in reference to people who identify with a specific geographic location, but currently reside elsewhere.

Notable diasporic populations include the Jewish diaspora formed after the Babylonian exile; Romani from the Indian subcontinent; Assyrian diaspora following the Assyrian genocide; Greeks that fled or were displaced following the fall of Constantinople and the later Greek genocide as well as the Istanbul pogroms; Anglo-Saxons (primarily to the Byzantine Empire) after the Norman Conquest of England; the Chinese diaspora and Indian diaspora who left their homelands during the 19th and 20th centuries; the Irish diaspora after the Great Famine; the Scottish diaspora that developed on a large scale after the Highland and Lowland Clearances; the Italian diaspora, the Mexican diaspora; the Circassian diaspora in the aftermath of the Circassian genocide; the Armenian diaspora following the Armenian genocide; the Palestinian diaspora; the Lebanese diaspora due to the Lebanese civil war; Syrians due to the Syrian civil war; and the Iranian diaspora which grew from half a million to 3.8 million between the 1979 revolution and 2019.

According to a 2019 United Nations report, the Indian diaspora is the world's largest diaspora, with a population of 17.5 million, followed by the Mexican diaspora, with a population of 11.8 million, and the Chinese diaspora, with a population of 10.7 million.

The term "diaspora" is derived from the Ancient Greek verb διασπείρω (diaspeirō), "I scatter", "I spread about" which in turn is composed of διά (dia), "between, through, across" and the verb σπείρω (speirō), "I sow, I scatter". The term διασπορά (diaspora) hence meant "scattering".

There is confusion over the exact process of derivation from these Ancient Greek verbs to the concept of diaspora. Many cite Thucydides (5th century BC) as the first to use the word. However, sociologist Stéphane Dufoix remarks "not only is the noun diaspora quite absent from the Greek original [Thucydides' Peloponnesian War, II, 27)], but the original does not include the verb diaspeírô either. The verb used is the verb speírô (seed) conjugated in the passive aorist." The passage in Thucydides reads:

καὶ οἱ μὲν αὐτῶν ἐνταῦθα ᾤκησαν, οἱ δ᾽ ἐσπάρησαν [esparēsan] κατὰ τὴν ἄλλην Ἑλλάδα, translated to mean 'Those of the Aeginetans who did not settle here were scattered over the rest of Hellas.'

Dufoix further notes, "Of all the occurrences of diaspora in the Thesaurus Linguae Graecae (TLG), which draws upon almost the entire written corpus in the Greek language . . . none refer to colonisation." Dufoix surmises that the confusion may stem from a comment by Jewish historian Simon Dubnow, who wrote an entry on diaspora for the influential Encyclopaedia of the Social Sciences. His entry, published in 1931, includes the following remark: "In a sense Magna Graecia constituted a Greek diaspora in the ancient Roman Empire." "Magna Graecia" refers to ancient Greek colonies established along the Italian coast, which lost their independence following the Second Punic War and their integration into the Roman Empire.

The first recorded use of the word "diaspora" is found in the Septuagint, first in: