Harp Mill is a former cotton spinning mill in the Castleton area of 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.