fourth surviving legitimate son of King Edward III of England and founder of the House of York (York, house of) as a branch of the Plantagenet dynasty.

Created earl of Cambridge in 1362 and duke of York in 1385, Edmund was the least able of Edward III's sons, and in the political strife of Richard II's reign he played an ineffective part. Between 1359 and 1378 he served without distinction in several campaigns in France, Spain, and Brittany, and his one independent command, the Lisbon expedition of 1381–82 to aid King Ferdinand of Portugal against Castile, was a failure. York was appointed keeper of the realm during Richard II's absence in Ireland in 1394–95, and again on the King's departure for his second Irish expedition in May 1399. When Henry of Lancaster (afterward King Henry IV) invaded England (July), York tried to organize resistance, but he soon submitted (July 27), recognizing that Richard's cause was lost.