Dolgoch is a narrow gauge 0-4-0 well tank steam locomotive. It was built by Fletcher, Jennings & Co. in 1866 and is one of the oldest locomotives still in active service. It was delivered to the Talyllyn Railway in 1866 and continues to run on this railway. Dolgoch holds an important place in railway preservation history as it was the only serviceable locomotive on the Talyllyn Railway when it became the first ever preserved railway to be operated by volunteers in 1951, and largely single-handedly kept the railway going during this first season.