The Penrhyn Quarry Railway was a six miles long narrow-gauge (1' 10¾") railway in Caernarfonshire, opened in June 1801, and was one of the earliest overground narrow gauge railways in the world. It was built to serve the Penrhyn quarry near Bethesda, and take the slate from the quarry to Port Penrhyn, near Bangor. The railway closed on 24 July 1962, the track being lifted in 1965 and sold to the Ffestiniog Railway.