Jagellon, a Polish royal family, founded by Jagello or Jagiello, a pagan grand duke of Lithuania, who embraced Christianity and became king of Poland under the name of Ladis-las II., consequent upon his marriage in 1386 with the Polish queen Hedvig, a daughter of Louis the Great, king of Hungary and Poland. He reigned till his death in 1434, and his dynasty, one of the best Poland ever had, expired with Sigismund Augustus in 1572; but the female line was perpetuated, through the marriage of the sister of Sigismund Augustus with Sigismund III., until the abdication of John II. Casimir, son of the latter (1668). Jagello's son Ladislas III. became king of Hungary under the name of Uladislas I., and a few other members of the family subsequently ruled over that country and over Bohemia, while intermarriage with the houses of Brandenburg, Saxony, and Brunswick established an extensive relationship between the Jagellons and many other dynasties. (See Hungary, Ladislas II., Lithuania, and Poland.)