German noblewoman, a Princess of Brandenburg and by marriage Electress of Saxony. From 1591 she was the regent of Saxony during the minority of her son Christian II.
Sophie was a daughter of the Elector of Brandenburg John George (1525–1598) by his second marriage with Sabina of Brandenburg-Ansbach (1548–1575), daughter of Margrave George of Brandenburg-Ansbach.
On 25 April 1582 in Dresden, Sophie married Elector Christian I of Saxony (1560–1591). Sophie was 14 years old at her wedding, and after a year she had her first child. They had the following children: Christian II (1583?1611, Elector), John George I (1585?1656, Elector of Saxony), Anna Sabine (1586-1586), Sophie (1587–1635), Elizabeth (1588?1589), Augustus (1589?1615), and Dorothea (1591?1617, Abbess of Quedlinburg).
After the death of her husband, who died at the age of only 31, Sophie, together with Duke Frederick William I of Saxe Weimar, became Regent of the Electorate for her eldest son.
Sophie was an orthodox Lutheran, and fought against crypto-Calvinism in Saxony. After Christian I’s death in 1591, she had the Calvinist Chancellor Nikolaus Krell, an opponent of Lutheran orthodoxy, imprisoned at the Königstein Fortress, and in 1601 had him executed at the Dresden Neumarkt. In allusion to the pious widow Judith in the Book of Judith, the orthodox Lutherans thereafter celebrated her as “Judith of Saxony”.
As a widow, Sophie lived in the so-called “Fraumutterhaus” in Dresden or in Castle Colditz. She had her own gold coins (“Sophie ducats”, Sophiendukaten) minted; she also had the old Franciscan church in Dresden again readied for divine service (1599–1610), which after her was called the Sophienkirche. The “Duchess’s Garden” (Der Herzogin Garten) also takes its name from Duchess Sophie. She died at Colditz Castle on 7 December 1622.

Link to Wikipedia biography