Edmund of Langley, 1st Duke of York (5 June 1341 – 1 August 1402) was the fourth surviving son of King Edward III of England and Philippa of Hainault.

He was the founder of the House of York, but it was through the marriage of his younger son, Richard of Conisburgh, 3rd Earl of Cambridge, to Anne de Mortimer, great-granddaughter of Edmund's elder brother Lionel of Antwerp, 1st Duke of Clarence, that the House of York made its claim to the English throne in the Wars of the Roses.

In 1359, he joined his father King Edward III on an unsuccessful military expedition to France and was made a knight of the Garter in 1361.

In 1369, he brought a retinue of 400 men-at-arms and 400 archers to serve with John Hastings, 2nd Earl of Pembroke, on campaigns in Brittany and Angoulême.

The following year, he first joined Pembroke again on an expedition to relieve the fortress of Belle Perche and then accompanied his eldest brother Edward, the Black Prince, on a campaign that resulted in the siege and sack of Limoges.

[3] Edmund acted as Keeper of the Realm in 1394/95 when his nephew, King Richard II of England, campaigned in Ireland and presided over Parliament in 1395.

He thereafter remained loyal to the new Lancastrian regime as Bolingbroke overthrew Richard II to become King Henry IV.

In the play, Edmund resigns his position as an adviser to his nephew Richard II, but is reluctant to betray the king.

After Bolingbroke deposes Richard and is crowned Henry IV, Edmund discovers a plot by his son Aumerle (Edward of Norwich) to assassinate the new king.