Llanmerewig is a historic parish in Powys, Wales, in the historic county of Montgomeryshire, and is situated between Newtown and Welshpool. The church and small village stand on high ground, which overlooks the river Severn, and is close to Abermule; part of which lies within the parish. The river Severn forms the North Western boundary of the parish and the Eastern boundary is the river Mule, which cuts through a steep gorge, before entering the Severn at Abermule. The historic parish covered 1,023 acres.