Roger Mortimer, 3rd Baron Mortimer of Wigmore, 1st Earl of March (25 April 1287 – 29 November 1330), was an English nobleman and powerful marcher lord who gained many estates in the Welsh Marches and Ireland following his advantageous marriage to the wealthy heiress Joan de Geneville, 2nd Baroness Geneville.

He was imprisoned in the Tower of London in 1322 for having led the marcher lords in a revolt against King Edward II in what became known as the Despenser War.

After he and Isabella led a successful invasion and rebellion, Edward was deposed; Mortimer allegedly arranged his murder at Berkeley Castle.

Roger attended the coronation of Edward II on 25 February 1308 and carried a table bearing the royal robes in the ceremony's procession.

During his lifetime Geoffrey also conveyed much of the remainder of his legacy, such as Kenlys, to his younger son Simon de Geneville, who had meanwhile become Baron of Culmullin through marriage to Joanna FitzLeon.

Shortly afterwards, at the head of a large army, he drove Bruce to Carrickfergus and the de Lacys into Connaught, wreaking vengeance on their adherents whenever they were to be found.

These acts of insurrection compelled the Lords Ordainers led by Thomas, 2nd Earl of Lancaster, to order the king to banish the Despensers in August.

When the king led a successful expedition in October against Margaret de Clare, Baroness Badlesmere, after she had refused Queen Isabella admittance to Leeds Castle, he used his victory and new popularity among the moderate lords and the people to summon the Despensers back to England.

[b] In the following year Queen Isabella, anxious to escape from her husband, obtained his consent to her going to France to use her influence with her brother, King Charles IV, in favour of peace.

King Charles IV's protection of Isabella at the French court from Despenser's would-be assassins played a large part in developing the relationship.

[c] In 1326, Mortimer moved as Prince Edward's guardian to Hainault, but only after a furious dispute with the queen, demanding she remain in France.

The suspicious death of Edward II has been the subject of many conspiracy theories, including that Mortimer's men killed him, but none has been proven.

[6] His own son Geoffrey, the only one to survive into old age, mocked him as "the king of folly" deriding his ambitious extravagance of "rich clothes ot of manner resoun, both of shaping and wearing".

[17] During his short time as ruler of England he took over the lordships of Denbigh, Oswestry and Clun (the first of which belonged to Despenser, the latter two had been the Earl of Arundel's).

The day Parliament opened on 15 October Thomas of Lancaster's nemesis, Sir Robert Holland was murdered by highway robbers.

The two earls' lethal enmity, and enforced absence from the King's presence, rendered their motives almost equally suspect to rowdy Londoners.

[19] Henry, Earl of Lancaster, one of the principals behind Edward II's deposition, tried to overthrow Mortimer, but the action was ineffective as the young king passively stood by.

Accused of assuming royal power and of various other high misdemeanours, he was condemned without trial and hanged at Tyburn on 29 November 1330, his vast estates forfeited to the crown.

[21] In 2002, the actor John Challis, the owner of the remaining buildings of Wigmore Abbey, invited the BBC programme House Detectives at Large to investigate his property.

During the investigation, a document was discovered in which Mortimer's widow Joan petitioned Edward III for the return of her husband's body so she could bury it at Wigmore Abbey.

Mortimer is also a character in Les Rois maudits (The Accursed Kings), a series of French historical novels by Maurice Druon.