Harlech Castle in Harlech, Gwynedd, Wales, is a Grade I listed medieval fortification built onto a rocky knoll close to the Irish Sea. It was built by Edward I during his invasion of Wales between 1282 and 1289 at the relatively modest cost of £8,190. Over the next few centuries, the castle played an important part in several wars, withstanding the siege of Madog ap Llywelyn between 1294 and 1295, but falling to Prince Owain Glyndŵr in 1404. It then became Glyndŵr's residence and military headquarters for the remainder of the uprising until being recaptured by English forces in 1409. During the 15th century Wars of the Roses, Harlech was held by the Lancastrians for seven years, before Yorkist troops forced its surrender in 1468, a siege memorialised in the song "Men of Harlech". Following the outbreak of the English Civil War in 1642, the castle was held by forces loyal to Charles I, holding out until 1647 when it became the last fortification to surrender to the Parliamentary armies. In the 21st century the ruined castle is managed by Cadw, the Welsh Government's historic environment service, as a tourist attraction.

Harlech is a seaside resort and community in Gwynedd, North Wales, and formerly in the historic county of Merionethshire. It lies on Tremadog Bay in the Snowdonia National Park. Before 1966, it belonged to the Meirionydd District of the 1974 County of Gwynedd. Its landmark Harlech Castle was begun in 1283 by Edward I of England, captured by Owain Glyndŵr, and in the 1480s, a stronghold of Henry Tudor. Once on a seaside cliff face, it is now half a mile inland. New housing has appeared in the low town and in the high town around the shopping street, church and castle. The two are linked by a steep road called "Twtil". Of its 1,447 inhabitants, 51 per cent habitually speak Welsh. The built-up area with Llanfair had a population of 1,762 in the 2001 census, over half of whom lacked Welsh identity, and the electoral ward which includes Talsarnau 1,997 in the 2011 census. The estimate in 2019 was 1,881. The population of the community, which includes just the village, was 1,263 as of the 2021 census.