After the passing the Statute of Rhuddlan (1284), which restricted Welsh laws, King Edward I's ring of impressive stone castles assisted in the domination of Wales, and he crowned his conquest by giving the title Prince of Wales to his son and heir in 1301. Wales became, effectively, part of England, even though its people spoke a different language and had a different culture. English kings appointed a Council of Wales, sometimes presided over by the heir to the throne. This Council normally sat in Ludlow, now in England but at that time still part of the disputed border area in the Welsh Marches. Welsh literature, particularly poetry, continued to flourish, however, with the lesser nobility now taking over from the princes as the patrons of the poets. Many consider Dafydd ap Gwilym, who flourished in the middle of the 14th century, the greatest of the Welsh poets.
There were a number of rebellions including ones led by Madog ap Llywelyn in 1294–1295 and by Llywelyn Bren, Lord of Senghenydd, in 1316–1318. In the 1370s the last representative in the male line of the ruling house of Gwynedd, Owain Lawgoch, twice planned an invasion of Wales with French support. The English government responded to the threat by sending an agent to assassinate Owain in Poitou in 1378.
In 1400, a Welsh nobleman, Owain Glyndŵr (or Owen Glendower), revolted against King Henry IV of England. Owain inflicted a number of defeats on the English forces and for a few years controlled most of Wales. Some of his achievements included holding the first ever Welsh Parliament at Machynlleth and plans for two universities. Eventually the king's forces were able to regain control of Wales and the rebellion died out, but Owain himself was never captured. His rebellion caused a great upsurge in Welsh identity and he was widely supported by Welsh people throughout the country.
As a response to Glyndŵr's rebellion, the English parliament passed the Penal Laws against Wales. These prohibited the Welsh from carrying arms, from holding office and from dwelling in fortified towns. These prohibitions also applied to Englishmen who married Welsh women. These laws remained in force after the rebellion, although in practice they were gradually relaxed.
In the Wars of the Roses which began in 1455 both sides made considerable use of Welsh troops. The main figures in Wales were the two Earls of Pembroke, the Yorkist Earl William Herbert and the Lancastrian Jasper Tudor. In 1485 Jasper's nephew, Henry Tudor, landed in Wales with a small force to launch his bid for the throne of England. Henry was of Welsh descent, counting princes such as Rhys ap Gruffydd (The Lord Rhys) among his ancestors, and his cause gained much support in Wales. Henry defeated King Richard III of England at the Battle of Bosworth with an army containing many Welsh soldiers and gained the throne as King Henry VII of England.
Under his son, Henry VIII of England, the Laws in Wales Acts 1535-1542 were passed, integrating Wales with England in legal terms, abolishing the Welsh legal system, and banning the Welsh language from any official role or status, but it did for the first time define the England-Wales border and allowed members representing constituencies in Wales to be elected to the English Parliament. They also abolished any legal distinction between the Welsh and the English, thereby effectively ending the Penal Code although this was not formally repealed.