Marcia Amelia Mary Pelham, Countess of Yarborough and 13th Baroness Conyers and 7th Baroness Fauconberg, OBE (18 October 1863 – 17 November 1926) was a British peer.
Marcia was the eldest daughter of the 12th Baron Conyers and his wife, Mary. On 5 August 1886, she married Charles Pelham, 4th Earl of Yarborough and they had four sons:
In 1888, the countess's father died and his title fell into abeyance, but the abeyance was terminated in her favour four years later. Eleven years later, in 1903, the barony of Fauconberg (a title which had been in abeyance since the death of the last holder, the 6th Baroness Fauconberg in 1490) was also granted to Marcia. The House of Lords also agreed that her father held the barony of Darcy de Knayth, which was granted to Marcia's sister, the Countess of Powis, at the same time. Due to the titles granted to her, Marcia brought 153 armorial quarterings to her husband's family.
In 1920, the countess was appointed an OBE in recognition of her role as Commandant of Brocklesby Park (her husband's ancestral home), which had been turned over as an auxiliary hospital during World War I. She died of sleeping sickness at Brocklesby in 1926 and her titles were inherited by her eldest surviving son, Sackville.