Furness ( /ˈfɜrnɨs/) is a peninsula in south Cumbria, England. At its widest extent, it is incorrectly considered to cover the whole of North Lonsdale, that part of the Lonsdale hundred that is an exclave of the historic county of Lancashire, lying to the north of Morecambe Bay.
The area is divided into Low Furness and High Furness. Low Furness is the peninsula; it juts out into the Irish Sea and delineates the western edge of Morecambe Bay. The southern end of the peninsula is dominated by the bay's tidal mudflats. The long thin island of Walney lies off the peninsula's south-west coast. High Furness is the northern part of the area, that was part of North Lonsdale but is not on the peninsula itself. Much of it is within the Lake District National Park, and contains the Furness Fells. It borders England's largest body of water, Windermere. Additionally, the Cartmel Peninsula is often included in definitions of Furness. Strictly speaking, however, Cartmel is not part of Furness, forming a separate peninsula between the estuaries of the rivers Leven and Kent.
The town of Barrow-in-Furness dominates the region with c.60% of the population. Other principal settlements of the region are Ulverston, Dalton-in-Furness, Coniston, Broughton-in-Furness, and Askam and Ireleth. The population of Furness stands at around 100,000.