Earl of Oxford and Earl Mortimer was a title in the Peerage of Great Britain. It was created in 1711 for the statesman Robert Harley, with remainder, failing heirs male of his body, to those of his grandfather, Sir Robert Harley. He was made Baron Harley, of Wigmore in the County of Hereford, at the same time, also in the Peerage of Great Britain and with similar remainder as for the earldom. Harley was the eldest son of Sir Edward Harley and the grandson of the aforementioned Sir Robert Harley.

Robert Harley, 1st Earl of Oxford and Earl Mortimer, KG PC FRS was an English statesman and peer of the late Stuart and early Georgian periods. He began his career as a Whig, before defecting to a new Tory ministry. He was raised to the peerage of Great Britain as an earl in 1711. Between 1711 and 1714 he served as Lord High Treasurer, effectively Queen Anne's chief minister. He has been called a prime minister, although it is generally accepted that the de facto first minister to be a prime minister was Robert Walpole in 1721.