Thames (tĕmz), a river of England rising in Cotswold Hills and flowing to the North Sea. It is about 220 miles long, and as far as London, 60 miles from its mouth, is navigable for large vessels. It is 18 miles wide at its mouth, and the tide flows up for 72 miles. The largest river of England, it also is the most important, having as large a traffic, probably, as any river in the world. Its bridges and tunnels at London, its great docks and embankments, are a part of the sights of the city. Canals connect it with the Avon and the Severn, the Sussex coast and the canal system of central England.