The Meic Uilleim (MacWilliams) were the Gaelic descendants of William fitz Duncan, grandson of Máel Coluim mac Donnchada, king of Scots. They were excluded from the succession by the descendants of Máel Coluim's son David I during the 12th century and raised a number of rebellions to vindicate their claims to the Mormaerdom of Moray and perhaps to the rule of Scotland.