She was married first in 589 to Authari, king of the Lombards, son of king Cleph. Authari died in 590. Theodelinda was allowed to pick Agilulf as her next husband and Authari's successor in 591. She thereafter exerted much influence in restoring Nicene Christianity (the mainstream, later split in 1054 by the East-West Schism in Roman Catholicism and Eastern Orthodoxy) to a position of primacy in Italy against its rival, Arian Christianity.
After the conversion of Agilulf to the Catholic faith, she started building churches in Lombardy and Tuscany, among them the cathedral of Monza and the first Baptistery of Florence. They were all dedicated to Saint John the Baptist.
The famous treasure of Monza contains the Iron Crown of Lombardy and the theca persica, enclosing a text from the Gospel of John, sent by Pope Gregory I (590-604) to her for her son Adaloald. Another of the gifts of this pope to the Lombard queen was a cruciform encolpion (reliquary) containing a portion of the True Cross. The history of the queen and her connection with the famous Iron Crown of Lombardy are narrated in the frescoes painted in the Theodelinda Chapel in the Monza Cathedral, work by Ambrogio and Gregorio Zavattari (1444).
- Herbermann, Charles, ed. (1913). "Lombardy". Catholic Encyclopedia. Robert Appleton Company.
- This article incorporates text from a publication now in the public domain: Herbermann, Charles, ed. (1913). "Lombardy". Catholic Encyclopedia. New York: Robert Appleton.