|Achnamara, Loch Sween, Knapdale, Argyll, Scotland|
Castle Sween, also known as Caisteal Suibhne, and Caistéal Suibhne, is located on the eastern shore of Loch Sween, in Knapdale, south of the forestry village of Achnamara on the west coast of Argyll, Scotland. Castle Sween is thought to be one of the earliest stone castles built in Scotland, having been built in the late 11th century. The castle's towers were later additions to wooden structures which have since vanished.
Castle Sween is the oldest stone castle in Scotland, built in the late 11th century by Suibhne, son of Hugh Anrahan, brother of the king of Ulster and High King of Ireland, from whom it takes its name Suibhne.
As late as the thirteenth century, the MacSweens possessed the surrounding lands of Knapdale. However, by the second half of the century, these territories passed into the hands of the Stewart/Menteith family.
In 1310, Edward II, King of England, granted John MacSween, and his brothers, the MacSweens' ancestral lands of Knapdale, provided that they oust John Menteith. It is possible that MacSween, and his claim to his family's lost Scottish homeland, may be the subject of the Gaelic poem Dál chabhlaigh ar Chaistéal Suibhne. If so, this poem may well refer to an expedition by MacSween to retake Castle Sween in about 1310.
In 1323, after the death of John Menteith, the Lordship of Arran and Knapdale passed to his son and grandson. In 1376, half of Knapdale, which included the castle, passed into the possession of John MacDonald I, Lord of the Isles, by a grant from his father-in-law, Robert II, King of Scotland.