John,_Duke_of_Östergötland--King_Carl_XVI_Gustaf

John of Sweden, Duke of Östergötland (in Swedish Johan) (18 April 1589 – 5 March 1618) was a Swedish royal dynast. He was titular Duke of Finland 1590–1606 and reigning Duke of Östergötland 1606–18.
His father was John III of Sweden and his mother was Gunilla Bielke. John's half-brother was King Sigismund III of Poland (1566–1632, reigned in Sweden in 1592–99, and in the Polish–Lithuanian Commonwealth in 1587–1632). His uncle was Charles IX of Sweden, who ruled from 1599 to 1611, and his first cousin was Gustav II Adolf of Sweden (1594–1632).