Holderness, low-lying peninsula and geographic region, geographic county of East Riding of Yorkshire, historic county of Yorkshire, England, between the River Humber estuary and the North Sea. The plain of Holderness terminates in a line of unstable clay cliffs along the coast of the North Sea to the east, where erosion is a serious problem north of Spurn Head, which is the peninsula’s southernmost tip. Several villages and their fields have been lost under the North Sea since Roman times, and costly seawalls protect the North Sea coastal resorts of Hornsea and Withernsea. Coastal currents have swept the eroded sediment and the mouth of the Humber south over the centuries to form the sand spit and mud flats at Spurn Head. Meanwhile, sediment from the River Humber has silted up many small harbours, such as Hedon, that were tidal in medieval times, and silt deposits to the south, such as Sunk Island, have been reclaimed in modern times as farmland.
Apart from Hornsea and Withernsea, the region is still profoundly rural. Since enclosure and piecemeal drainage of the hollows of its hummocky surface and the estuary silts were completed in the 19th century, Holderness has been one of the most productive agricultural regions in England, raising large crops of cereals as well as sugar beets and fodder crops and supporting a high density of livestock, including intensive pig and poultry enterprises. A gas terminal at Easington receives natural gas from offshore fields, and salt cavities beneath the clay surface near Hornsea have been excavated for large-scale storage.