For some ancient Jews, “diaspora” (together with its cognates) was an actor’s and not an observer’s term. But its import was primarily theological: God punished the Jews for their sins by dispersing them from their native land of Israel. Yet “diaspora” retains analytic utility for historians, if taken to refer to the geographically and temporally varied modes of Jewish life outside Palestine. It is not known to what extent diaspora Jews were emigrants from Palestine and their descendants; nor do we know how numerous they were. But we can follow the evidence where it exists. The main lesson is that the onset of Roman rule created crises around the integration of the Jews into their host societies. Intentionally or not, in the cities of the east (and the big villages of Egypt) the Romans fomented discord between different elements of the population. In Egypt, this led at once to the ultimately lethal—for the Jews, anyhow—three-way competition between Jews, Greeks, and Egyptians. Even in Asia Minor, normally understood as the best-case scenario for Jews under Roman rule, the evidence indicates that Jewish life in the Roman imperial period was more fragile, constrained, fraught, and impermanent than is often supposed.