Andronikos IV Palaiologos, Byzantine Emperor (d. 1385)
Andronikos IV Palaiologos or Andronicus IV Palaeologus (Greek: Ἀνδρόνικος Παλαιολόγος; 11 April 1348 – 25/28 June 1385) was the eldest son of Emperor John V Palaiologos. Appointed co-emperor since 1352, he had a troubled relationship with his father: he launched a failed rebellion in 1373, usurped the throne in 1376–1379, and remained engaged in a bitter struggle with John V until his death in 1385. This civil war depleted Byzantium's scarce resources and greatly facilitated the Ottoman conquest of the Balkans, most notably through the cession of Gallipoli by Andronikos.