Great Vlachia or Great Wallachia (Aromanian: Vlãhia Mari; Greek: Μεγάλη Βλαχία, romanized: Megálē Vlachía), also simply known as Vlachia (Aromanian: Vlãhia; Greek: Βλαχία, romanized: Vlachía), was a province and region in southeastern Thessaly in the late 12th century, and was used to denote the entire region of Thessaly in the 13th and 14th centuries. The name derives from the Vlachs (Aromanians), who had lived across much of the area.