James Mor Stewart, called James the Fat, (Scottish Gaelic: Seamas Mór) (c. 1400–1429 or 1449) was the youngest son of Murdoch Stewart, Duke of Albany and Isabella of Lennox. When his father and brothers were executed by King James I for treason in 1425, James led a rebellion against the king, taking the town of Dumbarton and killing the keeper of Dumbarton Castle. His success was short lived and he soon fled to Ireland, where he would spend the remainder of his life in exile. A second attempt at rebellion in 1429 saw a fleet sail to Ireland to collect James "to convey him home that he might be king", but he died before the attempt could be made.