Charles IX of Sweden, also Carl (; 4 October 1550 – 30 October 1611), was King of Sweden from 1604 until his death. He was the youngest son of King Gustav I of Sweden and his second wife, Margaret Leijonhufvud, brother of Eric XIV and John III, and uncle of Sigismund I/III, king of both Sweden and Poland. By his father's will he got, by way of appanage, the Duchy of Södermanland, which included the provinces of Närke and Värmland; but he did not come into actual possession of them till after the fall of Eric and the succession to the throne of John in 1568.