Clan Stewart of Appin is the West Highland branch of the Clan Stewart and have been a distinct clan since their establishment in the 15th century. Their Chiefs are descended from Sir James Stewart of Perston, who was himself the grandson of Alexander Stewart, the fourth High Steward of Scotland. His cousin Walter Stewart, the 6th High Steward, married Marjorie Bruce, the daughter of King Robert the Bruce, and their son Robert II was the first Stewart Monarch. The Stewarts of Appin are cousins to the Royal Stewart Monarchy.

Clan Stewart is a Scottish Highland and Lowland clan. The clan is recognised by Court of the Lord Lyon; however, it does not have a Clan Chief recognised by the Lord Lyon King of Arms. Because the clan has no chief it can be considered an armigerous clan; however, the Earls of Galloway are now considered to be the principal branch of this clan, and the crest and motto of The Earls of Galloway's arms are used in the Clan Stewart crest badge. The Court of the Lord Lyon recognises two other Stewart/Stuart clans, Clan Stuart of Bute and Clan Stewart of Appin. Clan Stuart of Bute is the only one of the three clans at present which has a recognised chief.