Roger Mortimer, 1st Baron Mortimer of Wigmore (c. 1231 – 27 October 1282), of Wigmore Castle in Herefordshire, was a marcher lord who was a loyal ally of King Henry III of England and at times an enemy, at times an ally, of Llywelyn ap Gruffudd, Prince of Wales.

In 1256 Roger went to war with Llywelyn ap Gruffudd when the latter invaded his lordship of Gwrtheyrnion or Rhayader.

Montfort's Welsh soldiers broke and ran for the bridge, where they were slaughtered by Mortimer's men.

Llewellyn's objections to Mortimer's construction of a new castle Cefnllys contributed to the climate of distrust that preceded Edward I's 1282 campaign.

Roger Mortimer died on 27 October 1282 at Kingsland, Herefordshire, and was buried at Wigmore Abbey, where his tombstone read: