Donnchad mac Maíl Coluim (Duncan II) was son of Máel Coluim mac Donnchada and his first wife Ingibiorg Finnsdottir, widow of Thorfinn Sigurdsson.
Donnchad was given into the keeping of William the Conqueror in 1072 as a hostage, and spent many years at court, where he was exposed to the newly arrived Norman culture. His father, who had many sons, appears to have made no effort to obtain Donnchad’s return. By the reign of William Rufus, Donnchad was probably a member of the Norman court rather than a hostage, and he was knighted by the English King.
His father’s chosen successor was Donnchad’s half-brother Edward, who died in the same combat during the invasion of Northumbria in 1093 as did king Máel Coluim. Máel Coluim was succeeded by his brother Domnall Bán and Máel Coluim’s other sons joined their half-brother Donnchad in England.
Donnchad received king William Rufus’s tacit support for the Scottish kingship, but the English king did not extend direct support as he planned a campaign in Normandy. It is probably in the period 1093–1094 that Donnchad married Octreda (or Ethelreda), daughter of Cospatrick of Northumbria, although an earlier betrothal has been proposed. Accompanied by his Anglo-Norman followers, and perhaps by his older half-brothers, Donnchad easily defeated Domnall Bán in the early summer of 1094, but appears to have had little support north of the Forth, being reliant on his Northumbrian, English and Norman allies.
A revolt later in 1094 was directed against Donnchad’s followers rather than the new king, but many of the Normans were killed and the rest sent away in order to settle the revolt. Domnall Bán’s supporters appear to have rallied again, and Donnchad was murdered late in 1094 by Máel Petair, Mormaer of Mearns. He was buried at Dunfermline Abbey.
His son by Octreda, William fitz Duncan, was a prominent figure during the reigns of Donnchad’s half-brothers Alexander and David.