The MacLennans are of ancient Celtic origin from Ireland, and in the mist of antiquity we find Lide MacLennan and his Clan of twelve hundred men in Ossianic poetry. The MacGillafinnens, or MacLennans, were titled Lords of Loch Erne, Tairg, and Muintir Peodachain. In Scotland they were appanaged land in Lorne, Mull, Tiree, and Iona. St. Adamans recorded they were occupying Glenshiel at an early date and were in residence at Eilean Donnan Castle before 1263. They spread to Strathearn in Perthshire, Kirkcudbright, Dumbarton and Galloway. In Kintail, they lived with their kin, the MacRuairis, who were granted ten davochs of Kintail by David II in 1342.

After raiding Tain and Chanonry in 1372 the Clan was defeated by the Frasers and MacRaes of Aird at Drumderfit, Black Isle. The sept name Lobban originated from this battle. A further reverse at Lagabraad Conon in 1481 of Chief Duncan and his Clan terminated the MacDonald association. The name Logan is from the Gaelic word Laggan, meaning low lying ground, and this sept provided the Knights Sir Robert and Sir Walter Logan who escorted King Robert the Bruce's heart to the Holy Land. Both died with Sir James Douglas fighting the Moors in Spain in 1329.

At an early date they held lands in Strathearn, Galloway, Ulster and later were Barons occupying Restalrig and Fast Castles. Geoffrey, son of Knight Logan c1150 took the name of his estate GASK from whom those of the name Gass descend. Duncan MacLennan of Strathearn, who is mentioned in the charter of Alexander II in 1217, became Laird of Bombie. This spelling over a period of time became MacLellan and there were no fewer than 14 Knights in Galloway at the beginning of the 15th Century.

The religious strife in Scotland and Ireland brought the Clan together. Chief Ruairidh Ban, Son of John MacGillafinnen, was in Holland around 1630 in connection with the flight of the Earls from Ireland. At the Battle of Auldearn in 1645, the Clan (Scottish, Irish and Logans) failed to receive the order to retreat; were isolated and cut down by the Duke Gordon's Cavalry; eighteen Captains of the Clan were killed; and brothers of the Chief (Donald and Duncan MacIan) died defending the Standard. In recognition of the outstanding bravery of gigantic red-haired Chief Rory Ban, he was offered an honourable surrender; however, he declined and was shot. As Bothwell observed, the MacRaes married the widows and became a considerable Clan. A hundred years later at the Battle of Culloden, only twelve of the Clan took part, including Roderick (grandson of Chief Rory), so the great losses at Auldearn were still obvious.