Mrnjava (Serbian: Мрњава^[a]) was a Serbian provincial nobleman,^[1] born in Zahumlje, a frontier province in the western Serbian Kingdom.^[2] Mrnjava is the eponymous founder of the notable Mrnjavčević family; his son Vukašin Mrnjavčević became the co-ruler of the Serbian Empire (1365–1371) as king during the fall of the Serbian Empire.^[2]

Mrnjava's father was "Mrnjan"^[3] (Latin: Mergnanus; fl. c. 1280-1289^[4][5]), a financial chancellor (Latin: camerarius, sr. kaznac, lit. chamberlain) who served the king and queen, Stephen Uroš I and Helen of Anjou, at the court at Trebinje (in the royal province of Travunia). Mavro Orbini wrote that the family hailed from Hum, and that the poor Mrnjava and his two sons, who later lived in Blagaj,^[6] quickly rose to prominence under Stephen Uroš IV Dušan who sent for them to come to his court.^[4] Possibly, the family had left Hum, which had been part of the Serbian Kingdom, after the Bosnian conquest of Hum (1326), and settled in Livno (where Vukašin was allegedly born).^[2] The family most likely supported Dušan's Bosnian campaign (1350^[7]), in which he saw to reconquer Hum.^[2]

The name of his wife is unknown. Modern historiography has confirmed that he fathered two sons:

• Uglješa Mrnjavčević (1320–1371), despot of Serres 1365–1371
• Vukašin Mrnjavčević (1320-1371), Lord of the Serbian Land, of the Greeks, and of the Western Provinces^[8] (King, co-ruler of Emperor Stephen Uroš V, 1365–1371)

Mavro Orbini (mid 16th century -1614) added a third son to his descendants. This hypothesis was supported Pavel Jozef Šafárik, but no third son is acknowledged in modern historiography:^[1]

• Gojko Mrnjavčević (d. 1371), logothete at the Serbian Imperial court

• Orbini, Mauro (1601). Il Regno de gli Slavi hoggi corrottamente detti Schiavoni. Pesaro: Apresso Girolamo Concordia.
• Орбин, Мавро (1968). Краљевство Словена. Београд: Српска књижевна задруга.
• Fine, John V.A. (1994). The Late Medieval Balkans: A Critical Survey from the Late Twelfth Century to the Ottoman Conquest. The University of Michigan Press. ISBN 0-472-08260-4.
• M.A. Vladislav Boskovic (2009), King Vukasin and the Disastrous Battle of Maritsa", GRIN Verlag, ISBN 978-3-640-49243-5
• Lee, Gerald Stanley (1906). The voice of the machines: an introduction to the twentieth century. The Mount Tom Press.
• Soulis, George Christos (1984). The Serbs and Byzantium during the reign of Tsar Stephen Dušan (1331-1355) and his successors. Dumbarton Oaks Library and Collection. ISBN 9780884021377.