John Mór Tanister

John Mór Tanister (Scottish Gaelic: Eòin Mòr Tànaiste or Iain MacDhòmhnaill, died 1427) was the second son of John Macdonald (John of Islay, Lord of the Isles) and Princess Margaret Stewart of Scotland, daughter of King Robert II. He is the founder of Clan MacDonald of Dunnyveg.

He was granted 120 merklands in Kintyre, with the castles of Dunaverty, Skipness and Airds and 60 merklands on Islay with the castle of Dunyvaig upon his father's death. Not being satisfied with his inheritance, he led a revolt against his brother Dómhnall Íle as John was recognized as the heir-apparent (tànaiste). The rebellion started in 1387 and went on into the 1390s, and John obtained the support of the powerful Clan MacLean kindred. However, John and the MacLeans were eventually forced to submit to Dómhnall, and by 1395 John Mór had been forced to flee into Ireland. There he entered the service of King Richard II of England in Antrim and later King Henry IV.

Through his marriage with Margaret Bisset, a daughter of the MacEoin Bisset, Lord of the Glens, according to MacDonald shanachies he received as the dowry the Glens and Rathlin Island in Ireland, then becoming known as Lord of Dunnyvaig and the Glens. In fact this is a later invention, for the MacEoin Bissets continued to hold the Glens of Antrim until at least as late as 1522, when the last known died in battle.

He led the reserve at the battle of Harlaw just north of Inverurie in Aberdeenshire on 24 July 1411 and later fought with Robert Stewart, Regent Albany who had forayed into Argyll to force his brother Dómhnall Íle to surrender.

John Mor was attacked and killed by James Campbell after a scheduled meeting at Ard-du, Islay in 1427. He is thought to have been buried at Finlaggan.