(1583– 1654), Swedish statesman, who played an important part in the Thirty Years’ War. He was born June 16, 1583, near Enköping, and educated at the universities of Rostock, Jena, and Wittenberg in Germany. In 1612 he was appointed chancellor of Sweden by Gustav II Adolph, king of Sweden. He negotiated peace settlements with Denmark in 1613, with Russia in 1617, and with Poland in 1623, and was appointed governor-general of the province of Prussia in 1626. Following the death of the king, Oxenstierna became the most powerful statesman in Swedish history: In January 1633, the diet designated him legate plenipotentiary in Germany, with absolute power over the vast territories conquered by the Swedish armies during the early phase of the Thirty Years’ War. In the same year he organized the Protestant princes of Germany into a mutual-assistance organization known as the League of Heilbronn. In 1636 he negotiated the Treaty of Wismar with France, whereby Sweden, whose resources had been severely strained as a result of its recurring wars, gained the promise of aid from France while making no major concessions or sacrifices.

Another of Oxenstierna’s brilliant achievements was the planning of the Danish War of 1643–45, which resulted in the Peace of Brömsebro, whereby Denmark, the hereditary enemy of Sweden, was stripped of power. During the minority of the young Christina, queen of Sweden, Oxenstierna as regent wielded almost absolute power in the foreign and domestic policies of his country. After the regency ended in 1644, however, disputes with the queen led to the decline of his power. He was created a count in 1645 and died in Stockholm on Aug. 28, 1654.