THURSO, a burgh of barony and seaport of Scotland, in the county of Caithness, on a bay of the same name on the southern shore of the Pentland Firth, 21 miles N.W. of Wick. It is irregularly laid out, but contains, especially in the suburbs, many neat and substantially built houses. The parish church is an elegant building; and the town has also a Free church, and places of worship for the Original Seceders, Baptists, and Independents, several schools, two public libraries, and a news-room. Linen and woollen cloth, leather, ropes, and fishing-nets are made here; fisheries of haddock, cod, and lobsters are carried on in the bay; and there is some trade in grain, cattle, sheep, and paving-stones. The bay is unfavourably situated, and too much exposed to the sea for being a resort of much shipping; and the town is consequently not likely to increase much in size or importance. A little to the east stands an old castle, the residence of Sir George Sinclair of Ulbster. Pop. (of the town) 2908; (of the parish) 5096.