Background
Giedraitis was born into the Giedraičiai family of Lithuanian nobility.
Giedraitis was born into the Giedraičiai family of Lithuanian nobility.
He studied at University of Königsberg (1550), Universities of Wittenberg and Tübingen (1560–1563), University of Leipzig (1563).
He actively combated Reformation implementing resolutions of Council of Trent in Samogitia. Bishop of Samogitia Jurgis Petkūnas died in 1574. Walerian Protasewicz, Bishop of Vilnius, protested this nepotism and instead promoted Giedraitis, who had a clear advantage of speaking Lithuanian and Samogitian.
After a two-year political struggle Giedraitis prevailed and was consecrated bishop on 16 January 1576.
He worked hard to end clerical abuses, strengthen churches and schools, and increase number of priests. He supported use of the Lithuanian language and encouraged all priests to use it for sermons.
He sponsored Mikalojus Daukša, who published Catechism (1595) and Postil (1599) in the Lithuanian language—the first Lithuanian books printed within the Grand Duchy of Lithuania. He also supported Maciej Stryjkowski, author of the first printed history of Lithuania.
He was ordained as a priest in 1571 and soon became a member of the diocesan chapter in Vilnius.