The word Thrace was established by the Greeks for referring to the Thracian tribes, from ancient Greek Thrake (Θρᾴκη), descending from Thrāix (Θρᾷξ). It referred originally to the Thracians, an ancient Indo-European people inhabiting Southeast Europe. The name Europe first referred to Thrace proper, prior to the term vastly extending to refer to its modern concept.  The region could have been named after the principal river there, Hebros, possibly from the Indo-European arg "white river" (the opposite of Vardar, meaning "black river"), According to an alternative theory, Hebros means "goat" in Thracian.
In Turkey, it is commonly referred to as Rumeli, Land of the Romans, owing to this region being the last part of the Eastern Roman Empire that was conquered by the Ottoman Empire.
In terms of ancient Greek mythology the name appears to derive from the heroine and sorceress Thrace, who was the daughter of Oceanus and Parthenope, and sister of Europa.