Castledawson is a village in County Londonderry, Northern Ireland. It is mostly within the townland of Shanemullagh, about four miles from th…Castledawson is a village in County Londonderry, Northern Ireland. It is mostly within the townland of Shanemullagh, about four miles from the north-western shore of Lough Neagh, and near the market town of Magherafelt. In the 2011 Census, it had a population of 2,289.