Sigebert I (c. 535 – c. 575) was the king of Austrasia from the death of his father in 561 to his own death. He was the third surviving son out of four of Clotaire I and Ingund. His reign found him mostly occupied with a successful civil war against his half brother, Chilperic.

When Clotaire I died in 561, his kingdom was divided, in accordance with Frankish custom, among his four sons: Sigebert became king of the northeastern portion, known as Austrasia, with its capital at Rheims, to which he added further territory on the death of his brother, Charibert, in 567 or 568; Charbiert himself had received the kingdom centred on Paris; Guntram received the Kingdom of Burgundy with its capital at Orléans; and the youngest son, the aforementiond Chilperic, received Soissons, which became Neustria when he received his share of Charibert's kingdom. Incursions by the Avars, a fierce nomadic tribe related to the Huns, caused Sigebert to move his capital from Rheims to Metz. He repelled their attacks twice, in 562 and c. 568.