Harp Mill was a former cotton spinning mill in the Castleton, Rochdale, Greater Manchester, England. Queensway, Castleton was a hub of cotton mills including the three 't', Th'Arrow, Th'Harp, and Th'Ensor. The 1908 Castleton map includes: Marland Cotton Mill, Castleton Cotton Mill, Globe Works (Textile Machinery), Arrow Cotton Mill, Harp Cotton Mill, Globe Leather Works, Castleton Size Works and Castleton Iron Works. Th'Harp was taken over by the Lancashire Cotton Corporation in the 1930s and passed to Courtaulds in 1964. The site now houses industrial units.