Theudebert I (French: Thibert or Théodebert) was the Merovingian king of Austrasia from 533 to his death in 548. He was the son of Theuderic I and the father of Theudebald.
During his father's reign, the young Theudebert had shown himself to be an able warrior. In about 516 he defeated a Danish army under King Chlochilaich (Hygelac of Beowulf) after it had raided northern Gaul. His reputation was further enhanced by a series of military campaigns in Septimania against the Visigoths.
Upon his father's death, Theudebert had to fight both his uncles Childebert and Clotaire to inherit his father's kingdom. In the end, his military prowess persuaded Childebert to abandon the dispute and adopt Theudebert as his heir. Together they campaigned against Clotaire but sued for peace after their armies were hit by storm.
As well as being renowned for his military prowess, Theudebert was lauded by contemporaries for his patronage of the Gallic Church. Gregory of Tours reserves special praise for him in this regard, but his piety is also mentioned by Fortunatus.
Theudebert died in the 14th year of his reign (at the end of 547 or the beginning of 548) and Theudebald, his son by Deuteria, succeeded him. In contrast to that experienced by many Merovingian kings, Theudebald's accession was peaceful.