Caernarfon Castle was constructed at Caernarfon in North Wales by King Edward I of England, following his conquest of the principality in 1283.
Edward I built castles and walled towns in North Wales to control the area following his conquest of the independent principality of Wales, in 1283. Llywelyn ap Gruffudd, prince of Wales, having rejected a bribe of one thousand pounds a year and an estate in England, if he would surrender his nation unreservedly to the king of England, had been lured into a trap on 11 December 1282, and put to death. His brother Dafydd ap Gruffudd had continued the struggle for continuing independence, but had been captured at Bera Mountain in the uplands above Garth Celyn, in June 1283. Edward surrounded and overshadowed Garth Celyn, the royal home and the headquarters of resistance to English domination, with Caernarfon and Conwy castles, and later Beaumaris Castle. The other fortress in the iron ring encirling Snowdonia was Harlech Castle.
Begun in 1283 after Snowdonia - the heartland of Gwynedd - had been overrun by the massive army, it reached something like its current state in 1323. It was never completed, and even today there are joints visible in several places on the internal walls ready to accept further walls which were never built. Contemporary records note that the castle's construction cost some £22,000 – an enormous sum at the time, equivalent to more than a year's income for the royal treasury. The castle's linear design is sophisticated by comparison with earlier British castles, and the walls are said to have been modelled on those of Constantinople, Edward being a keen Crusader. The castle dominates the Menai Strait.
In the uprising of 1294–1295, Caernarfon was besieged, but the garrison was supplied by sea and held out to be relieved in the spring of 1295. In 1403 and 1404 it withstood sieges by the forces of Owain Glyndŵr. During the English Civil War its Royalist garrison surrendered to Parliamentary forces in 1646.
The tradition of investing the heir of the monarch of Britain with the title of "Prince of Wales" began in 1301, when King Edward I of England, having completed the conquest of Wales, gave the title to his heir, Prince Edward (later King Edward II of England). According to a famous legend, the king had promised the rebellious Welsh natives that he would name "a prince born in Wales, who did not speak a word of English" and then produced his infant son to their surprise (and presumable chagrin); but the story may well be apocryphal, as it can only be traced to the 16th century. However, Edward II certainly was born at Caernarfon while his father was campaigning in Wales, and like all infants, could not at the time speak English. (Indeed, growing up in the royal court over the succeeding years his first language may well have been Norman French, not English.)
The castle was used again in 1911 for the investiture of the then Prince of Wales, the future Edward VIII of the United Kingdom, because of its past associations with the English crown. This set a precedent which was to be repeated in 1969 with the investiture of Charles, Prince of Wales.
The castle also houses the regimental museum of the Royal Welsh Fusiliers, and is part of the World Heritage Site "Castles and Town Walls of King Edward I in Gwynedd".
Edward II of England was born here, during the initial stages of the castle's construction in 1284.