Montgomeryshire, also known as Maldwyn (Welsh: Sir Drefaldwyn) is one of thirteen historic counties and a former administrative county of Wales. It is named after its county town, Montgomery, which in turn is named after one of William the Conqueror's main counsellors, Roger de Montgomerie, who was the 1st Earl of Shrewsbury.
Montgomeryshire today constitutes the northern part of the principal area of Powys. The population of Montgomeryshire was 59,474 according to the 2001 census.