Dagobert I (Latin: Dagobertus) was:
- king of Austrasia (623–634)
- king of all the Franks (629–634)
- king of Neustria and Burgundy (629–639)
He was the last king of the Merovingian dynasty to wield any real royal power.
Dagobert was the eldest son of Chlothar II and Haldetrude (575–604). Chlothar had reigned alone over all the Franks since 613. In 623, Chlothar was forced to make Dagobert king of Austrasia by the nobility of that region, who wanted a king of their own.
When Chlothar granted Austrasia to Dagobert, he initially excluded Alsace, the Vosges, and the Ardennes, but shortly thereafter the Austrasian nobility forced him to concede these regions to Dagobert. The rule of a Frank from the Austrasian heartland tied Alsace more closely to the Austrasian court. Dagobert created a new duchy (the later Duchy of Alsace) in southwest Austrasia to guard the region from Burgundian or Alemannic encroachments and ambitions. The duchy comprised the Vosges, the Burgundian Gate, and the Transjura. Dagobert made his courtier Gundoin the first duke of this new polity that was to last until the end of the Merovingian dynasty.
Upon the death of his father in 629, Dagobert inherited the Neustrian and Burgundian kingdoms. His half-brother Charibert, son of Sichilde, claimed Neustria but Dagobert opposed him. Brodulf, brother of Sichilde, petitioned Dagobert on behalf of his young nephew, but Dagobert assassinated him and gave the Aquitaine to his own younger sibling.
As king, Dagobert made Paris his capital. During his reign, he built the Altes Schloss in Meersburg (in modern Germany), which today is the oldest inhabited castle in that country. Devoutly religious, Dagobert was also responsible for the construction of the Saint Denis Basilica, at the site of a Benedictine monastery in Paris. He also appointed St. Arbogast bishop of Strasbourg.
Dagobert died in the abbey of Saint-Denis and was the first Frankish king to be buried in the Saint Denis Basilica, Paris.