Harlech (Welsh pronunciation: [ˈharlɛx]) is a town and seaside resort in Gwynedd, within the historical boundaries of Meirionnydd in northwest Wales. Lying on Tremadog Bay and within the Snowdonia National Park, it has a population of 1,447, of whom 51% speak Welsh. The town is located in the unitary authority of Gwynedd which was formed in 1996, from 1974 to 1996 it was in the Meirionydd District of the 1974 County of Gwynedd, and before 1974 it was in the historic county of Merionethshire.
The town is best known for the landmark Harlech Castle, begun in 1283 by Edward I of England, captured by Owain Glyndŵr, and later the stronghold of Henry Tudor. The castle was originally built next to the sea, but geological processes have changed the shape of the coastline, and the castle now lies on a cliff face, about half a mile (800 m) inland. The town has since developed with housing estates on the flat low town area and hillside properties in the high town around the shopping street, church, and castle. The two areas are linked by a steep and winding road called "Twtil".