Mattias Alexander von Ungern-Sternberg (3 March 1689 – 13 January 1763) was as Swedish military officer and politician. In his youth he fought in the War of the Spanish Succession and the Great Northern War. During the Age of Liberty, he was politically engaged in the Caps party and was elected Lord Marshal of the parliament, the Riksdag of the Estates, in 1742 and again in 1746. As a politician he was moderate and willing to compromise. His political activities benefitted his military career and he was promoted to field marshal in 1753. In 1757, he briefly commanded Swedish troops during the Pomeranian War but was quickly relieved of command following a lacklustre performance and retired to his family estate, Äs säteri, where he died in 1763.