The Festiniog Railway Letter Service is an officially authorised service within the United Kingdom railway system for posting and transmission of letters, and under certain circumstances also delivering the letters directly to intended recipients. The service operates on the Ffestiniog Railway and the Welsh Highland Railway in North Wales and similar services are operated on the Talyllyn Railway and other heritage railways in the UK. The service was also offered until 1984 by British Railways as successors to the many constituent railway companies that had in 1891 signed an agreement with the G.P.O. and it was BR that regulated the terms and the charges in conjunction with the post office.