BLYTH, a market town and seaport of Northumberland, England, in the parliamentary borough of Morpeth, 9 m. E.S.E. of that town, at the mouth of the river Blyth, on a branch of the North Eastern railway. Pop. of urban district (1901) 5472. This is the port for a considerable coal-mining district, and its harbour, on the south side of the river, is provided with mechanical appliances for shipping coal. There are five dry docks, and upwards of 11 m. of quayage. Timber is largely imported. Some shipbuilding and the manufacture of rope, sails and ship-fittings are carried on, and the fisheries are valuable. Blyth is also in considerable favour as a watering-place; there are a pleasant park, a pier, protecting the harbour, about 1 m. in length, and a sandy beach affording sea-bathing. The river Blyth rises near the village of Kirkheaton, and has an easterly course of about 25 m. through a deep, well-wooded and picturesque valley.