Margaret of Béarn (c. 1245–1319), also known as Marguerite de Béarn, was the Viscountess of Béarn in her own right from 1290 until 1319. She was the eldest daughter and heiress of Gaston VII, Viscount of Béarn, and Martha of Marsan.
In 1267, Margaret married Roger-Bernard III, Count of Foix. This marriage was a pivotal event in the history of the Pyrenean principalities, as it eventually merged the County of Foix with the Viscounty of Béarn, creating a significant and semi-autonomous power base in southern France.
Upon the death of her father in 1290, Margaret succeeded to the Viscounty of Béarn. Her succession was not without conflict; it was contested by her sister, Constance of Béarn, and her husband, as well as other regional lords. The ensuing legal and military disputes necessitated the intervention of the French crown. King Philip IV of France eventually ruled in favor of Margaret and her husband, Roger-Bernard III, securing their control over the territory.
During her reign, Margaret focused on maintaining the administrative integrity of Béarn and navigating the complex feudal loyalties owed to both the King of France and the King of England (who held the title of Duke of Aquitaine). Her tenure was characterized by the defense of Béarn's traditional "foros" (local laws and privileges).
Margaret of Béarn was succeeded by her son, Gaston I, Count of Foix and Viscount of Béarn. Her lineage continued to rule the combined territories, which remained a distinct political entity until the 17th century.