Owen inherited property in the north of Wales: he was the claimant through his mother to the lands of Rhys ap Gruffydd. He is believed to have studied law in London before serving with the forces of Henry Bolingbroke, an opponent of King Richard II of England, who later seized the throne and became King Henry IV.
On his return to Wales, he found that England's oppressive rule had paralysed the Welsh economy and aroused popular resentment. He married Margaret Hanmer, whose father, Sir David Hanmer, a judge, came of an English family that was totally integrated with the local population. They settled down to a peaceful and prosperous family life, but Owen was regarded by many as the man most likely to revive Welsh hopes of self-government.
In September 1400, a year after Bolingbroke usurped the throne, Glendower's feud with a neighbour, Reynold, Lord Grey of Ruthin, touched off an insurrection in north Wales. The insurgency quickly became a national struggle for Welsh independence.
Glendower formed strategic alliances with Henry's most powerful opponents. In 1402 he captured Edmund Mortimer, uncle of the 5th Earl of March and a claimant to the English throne. When the king refused to ransom Mortimer, Owen secured his support and married him off to one of his own daughters. He then allied himself with the Percy family (Henry Percy, 4th Earl of Northumberland, Sir Henry "Hotspur" Percy, and Thomas Percy, 2nd Earl of Worcester). The defeat of the Percys at the Battle of Shrewsbury in 1403 (in which Owen did not take part) was a temporary setback for the Welsh leader.
By 1404 he had gained control of most of Wales. Styling himself prince of Wales, he established an independent Welsh Parliament and began to formulate his own foreign and ecclesiastical policies.
In 1405 the tide of battle turned decisively against him. The failure of an expedition from France on his behalf (1405-6) weakened him. The recapture by the English of Aberystwyth (1408) and Harlech (1409) under Prince Henry, later Henry V, left him powerless. His allies in England were crushed. He was, however, active in guerrilla fighting as late as 1412. The actual date and place of his death is not known.
A movement known as Meibion Glyndwr (The sons of Glyndwr) grew up in Wales during the 1980s and 1990s, campaigning against the increasing number of second homes bought by outsiders in rural areas. Their methods included arson.
Glendower is the subject of several historical novels, including: