Otto Truchsess von Waldburg (25 February 1514 – 2 April 1573) was Prince-Bishop of Augsburg from 1543 until his death and a Cardinal of the Catholic Church.

Otto was born at Scheer Castle to the Swabian noble House of Waldburg, which, for their support in the German Peasants' War was vested with the title of a hereditary Imperial Seneschal (Truchsess) by Emperor Charles V in 1526.

Designated for an ecclesiastical career, he studied at the Universities of Tübingen, Dole, Padua, Bologna, where he received his degree of Doctor of Theology in 1534, and Pavia.

In 1541 he was appointed Imperial councillor and acted as a strong advocate of the Catholic faith against the Protestant Reformation at the 1542 Reichstag of Speyer.

Otto however urged on a military expedition against the revolting nobles, which the Emperor prepared by forging an alliance with the (Lutheran) Duke Maurice of Saxony, when the Protestants in 1546 sparked the Schmalkaldic War by a preventive strike against the town of Füssen, a possession of the Augsburg bishop.