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.

Earl of Galloway is a title in the Peerage of Scotland. It was created in 1623 for Alexander Stewart, 1st Lord Garlies, with remainder to his heirs male bearing the name and arms of Stewart. He had already been created Lord Garlies in the Peerage of Scotland in 1607, with remainder to the heirs male of his body succeeding to the estates of Garlies. This branch of the Stewart family were distant relatives of the Stewart Kings of Scotland.