Rhayader was, from 1894 to 1974, a rural district in the administrative county of Radnorshire, Wales. The district was formed by the Local Government Act 1894, based on the existing Rhayader Rural Sanitary District. The rural sanitary district had included the Brecknockshire parish of Llanwrthwl, and this was administered by Rhayader Rural District Council until 1934, when it was transferred to . The rural district comprised nine civil parishes: * Abbey Cwmhir * Cefnllys Rural * Llanbadarnfawr * Llanfihangel Helygen * Llansanffraid Cwmdeuddwr * Llanyre * Nantmel * Rhayader * St Harmon