Owain Glyndŵr (or Owain Glyn Dŵr, (c. 1349 or 1359 – c. 1416) is a Welsh ruler and the last native Welshman to hold the title Prince of Wales (Tywysog Cymru).

He instigates a fierce and long-running but ultimately unsuccessful revolt against the English rule of Wales.

Glyndŵr is a descendant of the Princes of Powys from his father Gruffydd Fychan II, hereditary Tywysog of Powys Fadog and Lord of Glyndyfrdwy, and of those of Deheubarth through his mother Elen ferch Tomas ap Llywelyn.

On 16 September 1400, Glyndŵr instigates the Welsh Revolt against the rule of Henry IV of England.

Although initially successful and rapidly gaining control of large areas of Wales, the uprising suffers from key weaknesses - particularly a lack of artillery, which makes capturing defended fortresses difficult, and ships, which make their coastlands vulnerable - and is eventually overborne by the superior resources of the English.

Glyndŵr is driven from his last strongholds in 1408-9 and the last documented sighting of him is in 1412.

He refuses to accept a pardon and despite large rewards being offered, is never betrayed to the English.

As a result, his ultimate fate remains a mystery.

Glyndŵr is a notable figure in the popular culture of both Wales and England, portrayed in William Shakespeare's play Henry IV, Part 1 (anglicised as Owen Glendower) as a wild and exotic man ruled by magic and emotion ("at my nativity, The front of heaven was full of fiery shapes, Of burning cressets, and at my birth The frame and huge foundation of the earth Shaked like a coward."

— Henry IV, Part 1, Act 3, scene 1).

In the late 19th century the Cymru Fydd movement recreated him as the father of Welsh nationalism, revising the historical image of him and joining him in popular memory as a national hero on par with King Arthur.

In 2000, celebrations were held all over Wales to commemorate the 600th anniversary of the Glyndŵr rising.

Owain came 23rd in a poll of 100 Greatest Britons in 2002, and 2nd in the 100 Welsh Heroes poll of 2003-04.