Sigebert III was the king of Austrasia from 634 to his death; around 656–660. He has been described as the first roi fainéant - do-nothing king - of the Merovingian dynasty. Sigebert was the eldest son of King Dagobert I and his concubine Ragnetrude and half-brother of King Clovis II.
His wife was Queen Chimnechild of Burgundy and their son was King Dagobert II. To satisfy the Austrasian aristocracy (who exercised a certain autonomy), Sigebert's father gave him the kingdom of Austrasia, although it remained part of the larger Frankish realm.