Dagobert II (Latin: Dagober(c)tus; Old English: Dægberht; died 679) was the Merovingian king of the Franks ruling in Austrasia from 675 or 676 until his death. He is one of the more obscure Merovingians. He has been considered a martyr since at least the ninth century.

None of the narrative histories of the Merovingian period give an account of Dagobert's reign, which must be reconstructed from several different sources. Upon the death of his father in 656, he was deprived of the succession and exiled to Ireland to live as a monk. His return to Austrasia was arranged by Wilfrid, bishop of York. He ascended the throne following the assassination of his cousin in 675. During his brief reign he made war on the neighbouring Frankish kingdom of Neustria, signed a peace treaty with the Lombard Kingdom in Italy and reintroduced gold coinage.

The only near-contemporary assessment of Dagobert's character portrays him as a tyrant. He antagonized the bishops and imposed new taxes. He was assassinated by a conspiracy of the highest nobility. He was succeeded by his cousin, Theuderic III, king of Neustria, against whom he had previously warred.