Donnchad II (died 1204), anglicized as Duncan II or Dunecan II, succeeded his father Duncan I as Earl of Fife in childhood. As a child of the previous mormaer, he was entitled to succeed his father through primogeniture, but not to lead his kin-group, Clann MacDuib. That probably fell to his cousin, Aed mac Gille Míchéil. Like previous mormaers of Fife, Duncan II was appointed Justiciar of Scotia (i.e. Scotland North of the Forth). Donnchad's minority also meant that Ferchar, Mormaer of Strathearn, took supreme place as head of the Gaelic nobility and guide for the boy-king Malcolm IV.

The scholar Geoffrey Barrow suggests that it was during Duncan's tenure that Beinn MacDuibh took its names, i.e. when Duncan II acquired land in that area (Barrow, 1980, 86). Duncan, like other mormaers of Fife, kept in close association with the king. His name is recorded, among other places, in a charter granted to the priory on the Isle of May.

Duncan's person was required to be a hostage following the defeat of William the Lion and the Treaty of Falaise, although in fact he certainly sent someone else in his place. (Barrow, 2003, 106).

On Christmas Day 1160, he married Ada (Ela/Hela/Adela) who is named in official documents as a close relative of King Malcolm IV, translated as a half-sister by his father Henry or niece from the Latin text.^[1][2][3] Malcolm IV's father Henry is believed to have had children prior to his marriage.^[4] Duncan II had three sons, Malcolm, Duncan, and David, two notably named for the Scottish kings. He had a fourth child, a daughter, whose name is unknown. The earls of Fife are considered to have been important allies of the Scottish kings from King David I onward. In 1152, on the death of Scottish King David I's son Henry of Scotland, Duncan I had escorted Malcolm IV, introducing him as the royal heir.^[5]

His son Malcolm succeeded him in 1204.