The Balts or Baltic peoples (People who live by the Baltic Sea), defined as speakers of one of the Baltic languages, a branch of the Indo-European language family, are descended from a group of Indo-European tribes who settled area between the Jutland peninsula in the west and Moscow, Oka and Volga rivers basins in the east. One of the features of Baltic languages is the number of conservative or archaic features retained. Among the Baltic peoples are modern Lithuanians, Latvians (including Latgalians) — all Eastern Balts — as well as the Prussians, Yotvingians and Galindians — the Western Balts — whose languages and cultures are now extinct.

Adam of Bremen was the first writer to use the term Baltic in its modern sense to mean the sea of that name. Although he must have been familiar with the ancient name, Balcia, meaning a supposed island in the Baltic Sea, and although he may have been aware of the Baltic words containing the stem balt-, "white", as "swamp", he reports that he followed the local use of balticus from baelt ("belt") because the sea stretches to the east "in modum baltei" ("in the manner of a belt"). This is the first reference to "the Baltic or Barbarian Sea, a day's journey from Hamburg."