The River Spen or Spen Beck, in West Yorkshire, England, is a tributary of the River Calder. It rises north of Cleckheaton, runs through Liversedge and flows into the Calder to the south of Dewsbury at Ravensthorpe. The average rainfall for the river valley of between 600–1000mm per annum when combined with the steep narrow river channel, makes the Spen susceptible to regular flooding. It is referred to in the names of the local parliamentary constituency, Spen Valley and the former local government district of Spenborough.