The Jagiellons (Jogailos, in original Lithuanian) were a royal dynasty originating in Lithuania that reigned in some Central European countries (present day Lithuania, Belarusia, Poland, Ukraine, Latvia, Estonia, Kaliningrad, parts of Russia, Hungary) between the 14th and 16th century.
Jagiellons were hereditary rulers of Poland and Lithuania.
Catherine Jagiellon, wife of John III of Sweden, was 11 years older than her husband, having remained unmarried into her thirties.
The Jagiellon dynasty (sometimes Jagiellonian, Jagiello or Jogailos) ruled as grand dukes of Lithuania from 1377 and as kings of Poland from 1386 until the death (1572) of the last male heir, Sigismund Augustus.
Jagiełło (originally Jogaila sometimes Jagiellon), Grand Duke of Lithuania and the founder of the dynasty, became king of Poland as Ladislaus II after converting to Christianity and marrying Jadwiga, second of Poland's Angevin rulers.
Sigismund's heir was his sister, Catherine Jagiellonica, who married John III Vasa of Sweden; as a result, the main branch of the Jagiellons merged with the House of Vasa, which ruled Poland from 1587 until 1668.