Willoughby Bertie, 3rd Earl of Abingdon (28 November 1692 – 10 June 1760) was an English peer.
He was the son of James Bertie of Stanwell in Middlesex and Elizabeth Willoughby, and nephew of Montagu Venables-Bertie, 2nd Earl of Abingdon. He matriculated at Corpus Christi College, Cambridge on 27 November 1707.
The Berties were Tories, with a strong electoral interest in Westbury, where the Earls of Abingdon were lords of the manor. At the 1715 general election in January, a double return was made for the seat, with the mayor of Westbury returning two Tories, Bertie and Francis Annesley, and the constable returning two Whigs, George Evans and Charles Allanson, who had been sponsored by Lord Cowper to challenge the Bertie interest. The return for Bertie and Annesley was initially accepted on 28 March 1715 and they were declared elected, but on petition, a number of their voters were disenfranchised, and Evans (who had since been created Baron Carbery) and Allanson were declared elected on 1 June. At the 1722 election, Bertie's father James was returned with Annesley; Willoughby did not stand for Parliament again.
He married Anna Maria Collins in August 1727 in Florence. They had nine children:
Willoughby succeeded his uncle as Earl of Abingdon in 1743. He remained a staunch Tory, as he declined to join the Oxfordshire association in defence of the Hanoverian succession during the Jacobite rising of 1745. In 1764, the trustees of his estate sold some of his manors in Oxfordshire: Wendlebury to Sir Edward Turner, 2nd Baronet, and Chesterton to George Spencer, 4th Duke of Marlborough. In Wiltshire, Marden was sold to George Willy and Patney to Robert Amor.