Jagiełło (Lithuanian: Jogaila; Ukrainian: Ягайло; Yahailo), b ca 1351 in Vilnius, d 1 June 1434 in Horodok (Lviv region). Grand duke of Lithuania (1377–81, 1382–92) and king of Poland (1386–1434), known as Władysław II. The son of Algirdas, he was the founder of a dynasty that ruled Poland until 1572. He concluded the Union of Krevo between the ruling houses of Poland and Lithuania in 1385 and, after marrying Queen Jadwiga in 1386, he was crowned king. In 1387 he officially made Lithuania a Catholic country. In 1392 he relinquished Lithuania to his cousin Vytautas the Great, although he formally remained grand duke. At the Battle of Grunwald (Tannenberg) in 1410, Jagiełło and Vytautas's Polish-Lithuanian-Ruthenian and other forces won a decisive victory over the Teutonic Knights. After Vytautas's death he fought his brother Švitrigaila over Podilia (1430–2). Under Jagiełło the annexation of Galicia by Poland was completed, the Polish gentry was granted greater property rights, and Lithuania and Ukraine were drawn into the Polish sphere of political and cultural influence. Viceroys replaced many hereditary princes as local rulers, and Catholic nobles had a privileged status.
[This article originally appeared in the Encyclopedia of Ukraine, vol. 2 (1988).]