town and borough (district), administrative county of Norfolk, England. The borough stretches for 15 miles (24 km) along the North Sea and includes agricultural tracts and marshes in its hinterland. The town of Great Yarmouth is the borough's administrative centre. This town stands on a sandbank across the mouth of Breydon Water, which is formed by the Rivers Yare, Bure, and Waveney. The town and the part of the borough north of Breydon Water belong to the historic county of Norfolk, while the area south of Breydon Water belongs to the historic county of Suffolk.

In ancient times the area now covered by the sandbar was sea, and Roman forts at Caister-on-Sea (north of present Greater Yarmouth town) and Burgh Castle (now several miles inland) stood on the coast. By Saxon times the Greater Yarmouth sandbank had accumulated and was inhabited. In 1208 King John granted the town its charter, and by the end of the 13th century it was walled. The old port town grew around narrow streets (rows) leading down to the river. The sandbank continued to expand southward, and in 1567 a Dutch engineer cut the present harbour entry. Historic edifices include the medieval parish church and the tollhouse.

Yarmouth is a major base for North Sea gas and oil exploration. It was a long-established herring port famous for its smoked herring, the Yarmouth bloater. In addition, the local economy has electronics, engineering, furniture making, brewing, and various other light industries. Yarmouth has also become a holiday resort and centre for boating on the Broads, with which Breydon Water is connected. Area borough, 67 square miles (174 square km). Pop. (2001) town, 58,032; borough, 90,813.