Lazar Hrebeljanović (Serbian Cyrillic: Лазар Хребељановић; c. 1329 – 15 June 1389) was a medieval Serbian ruler who created the largest and most powerful state on the territory of the disintegrated Serbian Empire. Lazar's state, referred to by historians as Moravian Serbia, comprised the basins of the Great Morava, West Morava, and South Morava rivers.