John (IV) de Mowbray, 1st Earl of Nottingham, 5th Baron Mowbray, 6th Baron Segrave (1 August 1365 – 12 January 1383), was an English peer. Born 1 August 1365 at Epworth in the Isle of Axholme, Lincolnshire, John de Mowbray was the elder son of John de Mowbray, 4th Baron Mowbray, and Elizabeth Segrave. He had a younger brother, Thomas de Mowbray, 1st Duke of Norfolk, and three sisters, Eleanor, Margaret and Joan (for details concerning his siblings, see the article on his father, John de Mowbray, 4th Baron Mowbray). He was styled 'cousin' by John of Gaunt, 1st Duke of Lancaster.