Roger Mortimer, 4th Earl of March

Roger de Mortimer, 4th Earl of March, 6th Earl of Ulster (11 April 1374 – 20 July 1398) was a great-grandson of King Edward III, descended from his second surviving son Lionel of Antwerp, Duke of Clarence, and was considered the heir presumptive to the childless King Richard II, his mother's first cousin. However he predeceased Richard II by two years, albeit leaving issue, in whose line the claim to the crown continued. Although two years after Mortimer's death the crown was seized from King Richard II by the House of Lancaster, descended from the third son of King Edward III, the Mortimer claim to the throne was realised eventually by the House of York, descended in the male line from the fourth and most junior son of King Edward III, on the basis that they had married Anne Mortimer, the daughter and eventual sole heiress of Roger de Mortimer, 4th Earl of March. This claim to the crown by the House of York on the basis of their descent via a female line from the second son of King Edward III was the substance of the Wars of the Roses, as the ruling House of Lancaster was descended only from the third son of King Edward III, albeit in a direct male line.

Roger Mortimer's father, the 3rd Earl of March, died in 1381, leaving the six-year-old Roger to succeed to his father's title. The wardship and marriage of Roger was acquired by Thomas Holland, 2nd Earl of Kent, who married him off to his daughter Alianore. During his lifetime, Mortimer spent much time in Ireland; he served several tenures as Lord Lieutenant of Ireland and died during The Battle of Kellistown/ An Cath Cell Osnadha (County Carlow). He was succeeded by his young son, Edmund Mortimer, 5th Earl of March.