Dagobert II (Latin: Dagober(c)tus;[1] Old English: Dægberht;[2] died 679) was a Merovingian king of the Franks, ruling in Austrasia from 675 or 676 until his death.

During his brief reign, he was at war with Neustria, signed a peace treaty with the Lombard Kingdom in Italy and reintroduced gold coinage.

He was assassinated by a conspiracy of the highest nobility and was succeeded by his cousin, Theuderic III, king of Neustria, against whom he had previously warred.

[4] According to the Book of the History of the Franks, which dates to 727, after Sigebert's death, Grimoald, the mayor of the palace and the most powerful official under the king, arranged for Dagobert to be tonsured and placed in the custody of Dido, bishop of Poitiers.

He wrote that a local oral tradition current at that time put Dagobert in the monastery of Slane, a conclusion accepted by some modern scholars.

[b] According to Stephen, Dagobert was exiled to Ireland "in his youth" and when his friends and relatives later learned that he was still living they asked Wilfrid to bring him to England and from there send him on to Austrasia.

There is little consensus on who the friends could have been, possibly Wulfoald, the mayor of the palace under Childeric II or Pippin of Herstal and Martin of Laon, who came to power, according to the Book of the History of the Franks, after "the deaths of kings", perhaps in 675; or even Ultan, abbot of Saint-Maur-des-Fossés, who was Irish himself and had connections in Ireland.

[8] Only one seventh-century work from within the Merovingian kingdoms, the Life of Abbess Sadalberga of Laon, mentions the reign of Dagobert, and then only in passing.

It records that Sadalberga moved her convent from the suburbs of Langres in northern Burgundy to the city of Laon because of forebodings, later proven true by "recent fighting between Kings Dagobert and Theuderic".

This event can be dated precisely because the only other source for it, the History of the Lombards written by Paul the Deacon towards the end of the eighth century, reports the appearance of a comet in August the same year.

[14] Paul, however, mistakenly places the pact in the reign of the Lombard king Grimoald, who died in 671, before Dagobert had even returned from Ireland.

In the charter, Dagobert refers to the donations made by his father, but does not mention that the monastery was founded by Grimoald, the man who had exiled him.

His gold tremissis broke with the old Frankish style and copied the cross potent on three steps of contemporary Byzantine solidi.

[15] In 679, while on his way to Rome to attend a church council, Wilfrid stayed at the court of Dagobert, who was grateful to the bishop for having facilitated his return from Ireland.

[7] According to the report in the Life of Wilfrid, Dagobert was a "destroyer of cities, despising the counsels of the magnates, reducing the people with taxation ... being contemptuous of God's churches and their bishops.

[20] The Life of Wilfrid is the only source to record Dagobert's assassination, but some corroboration comes from the fact that he was revered as a martyr in the Ardennes region before the end of the ninth century.

[5] In 872, the cult of Dagobert was brought to life (or revived) by Charles the Bald, king of West Francia (840–877), who had his relics translated to a specially built basilica in Stenay staffed with its own canons.

The endowment had passed at some point to Beatrice, wife of Godfrey III, Duke of Lower Lorraine, who in 1069 left it to the abbey of Gorze.

This day is given in the Life of Dagobert; in the now lost calendar of saints made for Emma, wife of King Lothair of France (954–986); and in the auctaria (local additions) to the Martyrology of Usuard from the area of modern Belgium.