John de Mowbray, 4th Baron Mowbray (24 June 1340–1368) was the son of John de Mowbray, 3rd Baron Mowbray and Joan of Lancaster, daughter of Henry, 3rd Earl of Lancaster.
He was born on 25 June 1340 at Epworth. As was the custom of lords at the time, de Mowbray served in the French wars. The 4th Baron took the cross and died in Thrace near Constantinople, fighting the Turks in 1368.
John de Mowbray married Elizabeth de Segrave, 5th Baroness Segrave, daughter of Sir John de Segrave, 4th Baron Segrave, and Margaret, Duchess of Norfolk on 25 March 1349.
John and Elizabeth had at least two sons, and several daughters:
John de Mowbray; succeeded his father to the barony and created Earl of Nottingham by Richard II.
Thomas de Mowbray; succeeded his brother and created 1st Duke of Norfolk.
Eleanor de Mowbray; married Roger la Warr, 3rd Baron De La Warr.
Margaret 'Eleanor' de Mowbray; married John de Welles, 5th Baron Welles.
Anne de Mowbray; became Abbess of Barking.
Joan de Mowbray; married Sir Thomas Grey.
Margaret de Mowbray; married Sir Reginald Lucy of Dallington, and had issue.