Roman Catholic partisan and champion of the Counter-Reformation in Switzerland who was one of the most important Swiss political leaders in the latter half of the 16th century.

Representative of the Catholic cantons at the Council of Trent (Trent, Council of) and at the courts of four popes—Paul IV, Pius IV, Gregory XIII, and Gregory XIV—Lussy devoted much of his life to the furtherance of papal interests. Serving in the army of the Papal States (1557) and later in that of Venice (1560), he secured a substantial fortune from the sale of Swiss mercenaries into the pope's service. Lussy was a personal friend of Charles Borromeo, cardinal archbishop of Milan, and played a major role in implementing the reforms of Trent in Catholic Switzerland. In his native Unterwalden, he ruled as a virtual dictator. He also served on numerous diplomatic missions, most frequently in the cause of Catholicism.