John Mowbray, 3rd Duke of Norfolk, KG, Earl Marshal (12 September 1415 – 6 November 1461) was a fifteenth-century English magnate who, despite having a relatively short political career, played a significant role in the early years of the Wars of the Roses.

As a minor he became a ward of King Henry VI and was placed under the protection of Humphrey, Duke of Gloucester, alongside whom Mowbray would later campaign in France.

Mowbray's marriage to Eleanor Bourchier in the early 1430s drew him into the highly partisan and complex politics of East Anglia, and he became the bitter rival of William de la Pole, Earl (later Duke) of Suffolk.

[10] Until his majority, the Mowbray lands were administered by the English exchequer to the benefit of the crown, at a time when the government was in dire need of cash,[11] due to the Hundred Years' War.

[6] For the good rewle and governaunce of my lord of Northfolk beyng in the Kynges ward, it semeth expedient that he as wele as tho that shall be a boute hys person kepe and observe as hit towcheth hem severally the rewle comprised in tharticles undir wryton ....[12] (I.e., For the benefit of the Duke of Norfolk as the King's ward, it is expedient that he and those with him obey the rules written below as far as he and his followers are affected by them) As a young adult, Mowbray appears to have been raucous and troublesome, and surrounded himself with equally unruly followers.

Although he shortly after returned to England, in June 1439 he was again back in Calais, at Oye,[6] escorting Archbishop John Kemp's diplomatic mission to the peace conference.

[25] For Mowbray, East Anglia as the focus of his landed authority was forced upon him since this was where the majority of his estates were located: much of his Lincolnshire inheritance was held by his mother as dower.

[39] The first saw him bound over for the significant amount of £10,000, and confined to living within the royal Household,[40] preventing him from returning to seek revenge in East Anglia.

[6] Likewise, apart from an appointment to commissions of oyer and terminer in Norwich in 1443 (after the suppression of Gladman's Insurrection), he received no other significant offices or patronage from the crown.

[47] Generally, though, says Helen Castor, Mowbray's influence "proved woefully inadequate" to protect and defend his retainers and tenants to the degree they could reasonably expect from their lord.

[59] This may have been the only occasion on which Mowbray personally sat on a local King's Bench commission as the hearing J.P.[60] The arbitration did not resolve their feud, and in 1447 Wingfield returned to the attack.

[64] In 1451 Mowbray and de Vere collaborated in the county of Suffolk while investigating suspected participants in Jack Cade's Rebellion, which had broken out the previous year.

[69] ... after the dethe of Henri Howard the sessions of pees were at Gippeswiche the Saturday next after Trinity Sunday last passed there being oure right trusty and right welbeloved cousin the Duc of Norff ... at the wyche tyme the said Duc as it is said seing that he might not doo endite the said lord Scrop nor noone of his maynee for the dethe of the said Howard .... Mowbray also forced the gaoler of Bury St Edmunds to release a man charged with murder into Mowbray's custody.

[72] The Earl of Oxford in particular wished to extend his landholdings from Essex into Suffolk,[6] while Lord Scales had been granted the remnants of de la Pole's affinity by Queen Margaret.

[6] In any case, the county of Norfolk already possessed a strong and relatively independent layer of wealthy gentry, including the Pastons, the Howards and those around John Fastolf.

Jack Cade's rebellion in 1450—directly aimed at royal favourites like de la Pole—explicitly named Mowbray as one of the King's "natural counsellors" necessary to reform the realm.

[6] Mowbray gathered his forces at Ipswich on 8 November (having ordered John Paston to meet him there "with as many clenly people as ye may get"), and may have travelled into London with York, who had also recruited locally.

[84] Mowbray was appointed, with the Duke of York and Earl of Devon, to maintain law and order in the City of London for the duration of the parliament,[85] though his retinue caused as much trouble as it prevented.

[86] Certayn notable knyghtis and squyers of this countee theer to have comonyngs with your good Lordshep (the earl of Oxford) for the sad rule and governaunce of this counte, (Norfolk) wych standyth ryght indisposed.

In 1453, with the King incapacitated and York protector, Mowbray presented charges against Somerset in parliament, attacking his failure to prevent the loss of the "two so noble Duchies of Normandy and Guyenne" in France.

An uneasy peace existed between the court and the Yorkists until April 1455, when the King summoned a Great Council to meet at Leicester the following month.

[6][note 22] After four years of peace, the civil war resumed in September 1459 when the Yorkist Earl of Salisbury fought off a royal ambush at the Battle of Blore Heath.

He may have faced difficulty in mustering troops; the army recently raised to fight at St Alban's had been dispersed and this would require re-mustering.

[129] A contemporary chronicler described the situation thus So did The White Lion [Mowbray] full worthily he wrought, Almighty Jesus bless his soul, that their armies taught.

About noon the aforesaid John, Duke of Norfolk, with a fresh band of good men of war came to the aid of the newly elected King Edward ....[132]Mowbray launched a decisive attack on the Lancastrian flank, turning them left.

The couple appears to have shared a close bond: while travelling in 1451, Mowbray supposedly dispensed with his retinue to enjoy, according to Colin Richmond, "a private tryst" with his wife.

"[6] In contrast, Michael Hicks believes that honour was clearly important to Mowbray, as his pursuit of Somerset (for that duke's abject performance in France) shows.

In the 1960 BBC TV serial An Age of Kings, the character appears in the episode "Henry VI: The Morning's War" portrayed by Jeffry Wickham.

In the Elizabethan play The Merry Devil of Edmonton, Mowbray does not appear as a character on stage, but the comical figure Blague repeatedly claims that: "I serve the good Duke of Norfolk.

The 20th-century Shakespeare scholar W. W. Greg places it in the reign of Henry VI, basing his conclusion in part on Thomas Fuller's posthumously published History of the Worthies of England (1662).