Owain Glyndŵr Day is an unofficial holiday celebrated in Wales every September 16, honoring Owain Glyndŵr, the last native Welshman to hold the title Prince of Wales and a national hero. The day commemorates his proclamation as Prince of Wales in 1400, which marked the beginning of a significant rebellion against King Richard II that lasted over a decade. Glyndŵr's revolt was a response to the consolidation of power by the English monarchy, which accused him of treason. Although he disappeared in 1412 and is presumed to have died in 1415, legends suggest he awaits a call to return and liberate his people. The late 19th-century Cymru Fydd movement recognized Glyndŵr as the father of Welsh nationalism, and in 2000, the 600th anniversary of his uprising was celebrated across Wales. While a campaign to establish Owain Glyndŵr Day as a public holiday has not yet succeeded, some individuals observe the day unofficially.