Caithness, the most northern county of Scotland, bounded N. by the Atlantic ocean and Pentland firth, E. and S. E. by the North sea, and W. by Sutherlandshire; area, 712 sq. m.; pop. in 1871, 39,989, partly of Scandinavian descent. The extreme length is about 53 m.; extreme breadth, 33 m. Two thirds of the surface is flat moorland, devoid of trees, and with scanty vegetation. It rises gradually from the north and east to the ridge of hills on the border of Sutherlandshire, Morven, the highest peak, being 2,334 ft. There are many small lakes in the interior; the Reay, Thurso, and Wick are the principal streams. The climate is not severely cold, but in winter the storms are violent. The soil is light and sandy, but much of it is tolerably productive. The principal crops are oats, beans, flax, and potatoes. The fisheries are important, herring, cod, and ling being obtained in abundance off the coast; salmon abound in the streams, and trout in the inland lakes. The county is divided into 13 parishes, and returns a member to parliament. It gives the title of earl to the Sinclair family, and contains the castles of several noblemen.

The principal town is Wick, on the E. coast, which has a commodious harbor and considerable trade.