The Moravian Thaya (German: Mährische Thaya, Czech: Moravská Dyje) is a river in the Czech Republic and in Austria, and a 68.2 kilometres (42.4 mi) left tributary of the Thaya.
The Moravian Thaya originates about 4 kilometres (2.5 mi) southeast of Třešť near the village of Stajiště. From there it flows southward through or near the communities of Bezděkov, Panenská Rozsíčka, Urbanov, Žatec, Dyjice, Radkov, Slaviboř, and Černíč in the Vysočina Region. Further south it passes the South Bohemian settlements of Velký Pěčín, Dačice, Toužín, Hradišťko, Vnorovice, Staré Hobzí, Janov, Nové Hobzí, Modletice, Nové Sady, and Písečné before crossing the border into Austria.
In Austria, it joins the German Thaya at the city of Raabs an der Thaya. From there, the unified Thaya river flows generally eastward and re-enters the Czech Republic.