Todmorden is a market town and civil parish[3] in the Upper Calder Valley in Calderdale, West Yorkshire, England. It is 17 miles (27 kilometres) north east of Manchester and in 2011 had a population of 15,481.[4]

Todmorden is at the confluence of three steep-sided Pennine valleys and is surrounded by moorlands with outcrops of sandblasted gritstone.

The historic boundary between Yorkshire and Lancashire is the River Calder and its tributary, the Walsden Water, which run through the town. The administrative border was altered by the Local Government Act 1888 placing the whole of the town within the West Riding.

Throughout the first decade of the 20th century, the population of the Borough of Todmorden remained constant. The ten-yearly UK census returns show figures of 25,418 in 1901 and 25,404 in 1911. Like the rest of the Upper Calder Valley, Todmorden's economy experienced a slow decline from around the end of the First World War onwards, accelerating after the Second World War until around the late 1970s. During this period there was a painful restructuring of the local economy with the closure of mills and the demise of heavy industry.

On 1 January 1907, Todmorden Corporation became only the second municipality in the British Isles to operate a motor bus service. By the end of that year, the fleet had expanded to five double-deck vehicles: two by Critchley-Norris, two by Lancashire Steam (predecessor of Leyland Motors) and one by Ryknield. In 1931, the service became jointly operated by the Corporation and the LMS railway under the name "Todmorden Joint Omnibus Committee". At its maximum size in the 1940s and 1950s, the undertaking operated 40 vehicles over 50 route miles (80 km) through the rugged South Pennine terrain.

Until 1996, when postal counties were abolished, Todmorden's official postal county was Lancashire.