Strangford Castle is a castle on a height overlooking the harbour in Strangford, County Down, Northern Ireland, across Strangford Lough from Portaferry Castle. It was probably originally built in the 15th century but most of the present building dates from the late 16th century. Strangford Castle tower house is a State Care Historic Monument in the townland of Strangford Lower, in Down District Council area, at grid ref: J5887 4983.