Clan Robertson, is correctly known as Clan Donnachaidh (Scottish Gaelic: Clann Donnchaidh) is a Scottish clan. The principal surnames of the clan are Robertson, Reid and Duncan but there are also many other septs.

Origins

There are two main theories as to the origins of the Clan:

That the founder of the clan, Donn(a)chadh (Duncan) was the second son of Angus MacDonald, Lord of the Isles.
That the Robertsons are lineal descendants of the Celtic Earls of Atholl, whose progenitor was King Duncan I (Donnchadh in Scottish Gaelic).The Collins Scottish Clan & Family Encyclopedia supports this theory.