Williamstown is a village in Rhondda Cynon Taf, Wales.
It is situated within the CF40 postcode district, which is within the Tonypandy post town.
CF40 is the only postcode district within the Tonypandy post town.
The Tonypandy post town is within the Cardiff postcode area.
Administrative Ward: Pen-y-graig
Administrative District: Rhondda Cynon Taf
Country: Wales
UK Parliament: Rhondda