The Thracian Sea (Greek: Θρακικό Πέλαγος, Thrakiko Pelagos; Turkish: Trakya Denizi, "Тракийско море" - Bulgarian language) is the northernmost part of the Aegean Sea.

Its length from east to west is from 23°E to about 25.8°E, or from the Strymonian Gulf east to the northernmost part of the Gallipoli peninsula and the width from north to south is about 40.25°N to 41°N, or from the Dardanelles north to the boundary between the Xanthi and the Rhodope regional units.

Islands in the Thracian Sea include Thasos and Samothrace in Greece, and Gökçeada (Imvros in Greek) in Turkey.

In the south, the sea extends to the north coast of the island of Lemnos.

[citation needed] The northern part of the Thracian Sea is a habitat for the endangered Black Sea harbor porpoise (Phocoena phocoena relicta).