Tulcea County is a county (județ) of Romania, in the historical region Dobruja, with the capital city at Tulcea. It includes in its northeast corner the large and thinly-populated estuary of the Danube.

Dobruja or Dobrudja is a geographical and historical region in Southeastern Europe that has been divided since the 19th century between the territories of Bulgaria and Romania. It is situated between the lower Danube River and the Black Sea, and includes the Danube Delta, the Romanian coast, and the northernmost part of the Bulgarian coast. The territory of Dobruja is made up of Northern Dobruja, which is a part of Romania, and Southern Dobruja, which is a part of Bulgaria.