At the time of the Norman conquest of England in 1066, the dominant ruler in Wales was Bleddyn ap Cynfyn, who was king of Gwynedd and Powys. The initial Norman successes were in the south, where William Fitz Osbern overran Gwent before 1070. By 1074 the forces of the Earl of Shrewsbury were ravaging Deheubarth.
The killing of Bleddyn ap Cynfyn in 1075 led to civil war and gave the Normans an opportunity to seize lands in North Wales. In 1081 Gruffydd ap Cynan, who had just won the throne of Gwynedd from Trahaearn ap Caradog at the Battle of Mynydd Carn was enticed to a meeting with the Earls of Chester and Shrewsbury and promptly seized and imprisoned, leading to the seizure of much of Gwynedd by the Normans. In the south, Iestyn ab Gwrgant, the last ruler of the kingdom of Morgannwg, was deposed about 1090 by Robert Fitzhamon, lord of Gloucester, who established a lordship based in Cardiff and subsequently conquered the lowland part of Glamorgan. Rhys ap Tewdwr of Deheubarth was killed in 1093 while resisting Norman encroachment in Brycheiniog, and his kingdom was seized and divided between various Norman lordships. The Norman conquest of Wales appeared virtually complete.
In 1094 however there was a general Welsh revolt against Norman rule, and gradually territories were won back. Gruffydd ap Cynan was eventually able to build a strong kingdom in Gwynedd. His son, Owain Gwynedd, allied with Gruffydd ap Rhys of Deheubarth won a crushing victory over the Normans at the Battle of Crug Mawr in 1136 and annexed Ceredigion. Owain followed his father on the throne of Gwynedd the following year and ruled until his death in 1170. He was able to profit from disunity in England, where Stephen of Blois and the Empress Matilda were engaged in a struggle for the throne, to extend the borders of Gwynedd further east than ever before.
Powys also had a strong ruler at this time in Madog ap Maredudd, but when his death in 1160 was quickly followed by the death of his heir, Llywelyn ap Madog, Powys was split into two parts and never subsequently reunited. In the south, Gruffydd ap Rhys was killed in 1137, but his four sons, who all ruled Deheubarth in turn, were eventually able to win back most of their grandfather's kingdom from the Normans. The youngest of the four, Rhys ap Gruffydd (The Lord Rhys) ruled from 1155 to 1193. In 1171 Rhys met Henry II and came to an agreement with him whereby Rhys had to pay a tribute but was confirmed in all his conquests and was later named Justiciar of South Wales. Rhys held a festival of poetry and song at his court at Cardigan over Christmas 1176 which is generally regarded as the first recorded Eisteddfod. After Owain Gwynedd's death led to the splitting of Gwynedd between his sons, Rhys made Deheubarth dominant in Wales for a time.
Out of the power struggle in Gwynedd eventually arose one of the greatest of Welsh leaders, Llywelyn ab Iorwerth, also known as Llywelyn Fawr (the Great), who was sole ruler of Gwynedd by 1200 and by his death in 1240 was effectively ruler of much of Wales. Llywelyn made his 'capital' and headquarters at Garth Celyn on the north coast, overlooking the Menai Strait. His son Dafydd ap Llywelyn followed him as ruler of Gwynedd, but the king would not allow him to inherit his father's position elsewhere in Wales. War broke out in 1245, and the issue was still in the balance when Dafydd died suddenly at the royal home Garth Celyn, Aber Garth Celyn, Gwynedd without leaving an heir in early 1246. Llywelyn the Great's other son, Gruffudd had been killed trying to escape from the Tower of London in 1244. Gruffudd had left four sons, and a period of internal conflict between three of these ended in the rise to power of Llywelyn ap Gruffydd (also known as Llywelyn the Last Leader). The Treaty of Montgomery in 1267 gave Llywelyn control, directly or indirectly, over a large part of Wales. However, Llywelyn's ambition in uniting Wales under his leadership conflicted with Edward I of England's ambitions in Wales, and war followed in 1277. Llywelyn was obliged to seek terms, and the Treaty of Aberconwy greatly restricted his authority. War broke out again when Llywelyn's brother Dafydd ap Gruffudd attacked Hawarden Castle on Palm Sunday 1282. Llywelyn appears to have hesitated before joining the rising, but eventually supported his brother. On 11 December 1282, Llywelyn was lured into a meeting in Builth Wells Castle with the Mortimer Brothers, captured and executed. His brother Dafydd ap Gruffudd continued the resistance, but was no match for the expensively equipped English army. He was captured at Bera Mountain, in the uplands above Aber Garth Celyn in June 1283 and was hanged, drawn and quartered at Shrewsbury. In effect Wales became England's first colony until it was finally annexed through the Laws in Wales Acts 1535-1542.