Jovan Uglješa (Serbian Cyrillic: Јован Угљеша; fl. 1346–1371) was a Serbian medieval nobleman of the Mrnjavčević family and one of the most prominent magnates of the Serbian Empire. He held the title of despot, received from Serbian Emperor Stefan Uroš V, whose co-ruler - Serbian King Vukašin was Uglješa's brother.
Uglješa was the son of Mrnjava, a treasurer of Helen, the queen consort of Stephen Uroš I of Serbia. He held Travunija in 1346, during the rule of Stefan Dušan (1331–1355). Uglješa married Jelena (later nun Jefimija), daughter of Vojihna, the kesar of Drama. This boosted the power of Uglješa, who would later govern the region alongside his father-in-law. Vojihna died in 1360, and his lands were inherited by Uglješa. He was given the title of despotes by the widowed Serbian empress, Helena of Bulgaria, in 1365. His domain, the Principality of Serres [bg], was situated along the lower course of the Struma with Serres as seat, eventually replacing Helena in its possession. From 1368, his territory was under the religious jurisdiction of the Ecumenical Patriarchate of Constantinople. The Patriarch mentioned the "master of Raška" (another name for Serbia), Jovan Uglješa, in a letter from 1371. With the Ottoman threat rising in the Balkans, Uglješa and his brothers Vukašin Mrnjavčević and Gojko Mrnjavčević tried to oppose the Turks. Uglješa was killed on 26 September 1371 in the Battle of Maritsa. Their troops were defeated by those of Ottoman commanders Lala Shahin Pasha and Gazi Evrenos at the Battle of Maritsa in 1371. The defeat resulted in large portions of the region of Macedonia falling under Ottoman power. Additionally, Uglješa's two brothers were killed during the fight. Their courage made them heroes of Bulgarian and Serbian epic poetry.
