Sigebert III (c. 630–656) was the Merovingian king of Austrasia from 633 to his death around 656. He was described as the first Merovingian roi fainéant —do-nothing king—, in effect the mayor of the palace ruling the kingdom throughout his reign. However he lived a pious Christian life and was later sanctified, being remembered as Saint Sigebert of Austrasia in the Roman Catholic Church and Eastern Orthodox Church.