Frederick Ponsonby, 3rd Earl of Bessborough

British peer and politician (1758–1844)

Frederick Ponsonby, 3rd Earl of Bessborough (24 January 1758 – 3 February 1844), styled the Viscount Duncannon from 1758 to 1793, was an Anglo Irish peer.

Ponsonby was the eldest son of Viscount Duncannon (who succeeded as the 2nd Earl of Bessborough in July 1758) and Lady Caroline Cavendish, daughter of The 3rd Duke of Devonshire. He succeeded to his father's titles in 1793. He was educated at Christ Church, Oxford, and obtained the degrees of Master of Arts and Doctor of Civil Law. As Viscount Duncannon, he sat in the House of Commons as member for Knaresborough from 1780 until his succession to his father's earldom. He was a Lord of the Admiralty in 1782–83.

On 27 November 1780, Duncannon married the intelligent and kind Lady Henrietta Spencer, second daughter of John Spencer, 1st Earl Spencer. Duncannon and Harriet had four children: Tired of Duncannon's vacillating abusive temper, and craving for love in her life, Harriet started a disastrous affair with Richard Brinsley Sheridan. This affair was indeed disastrous for Harriet, as the worst case scenario actually happened: the abusive Duncannon walked in on Harriet and Sheridan having intercourse. Violently enraged, Duncannon immediately wanted to divorce Harriet. Divorce in the 18th century was social ruin for women, and Harriet narrowly escaped such calamity only when Duncannon's father William Ponsonby, 2nd Earl of Bessborough and the powerful Cavendish clan sided with Harriet, making divorcing her social suicide. Perhaps chastened by time and age, by 1820 Duncannon rather miraculously ceased his abuse, and he and Harriet eventually settled into a companionable marriage. In 1821, Harriet died suddenly of a "chill" caught while travelling in Italy. Duncannon was heartbroken by her death. He outlived her by more than 20 years, dying at Canford House, Dorset, in 1844.

Duncannon usually made a favourable first impression: quiet, but with "the most mild and amiable manner". On the other hand, he was a notoriously cruel husband, fluctuating between sweet or obsessive attentiveness, neglecting Harriet entirely, or physically abusing her. His abuse of his wife was so public his family could not keep up appearances by pretending it was not occurring. In 1791 Harriet's serious illness gave rise to rumours, apparently quite unfounded, that he was trying to kill her. Like most of the Ton (le bon ton), Duncannon was a gambling addict. When he would lose, he would erupt into rages that terrified his wife. Duncannon's abuse and his gambling rages made Harriet's family fearful for her safety. Their fears were often proven, as when he threatened violence if Harriet did not hand over her marriage settlement to him after losing an especially ruinous gambling round. Luckily for the terrified Harriet, her kind brother George Spencer, 2nd Earl Spencer swept in and protected her from immediate violence by quietly giving Duncannon the money.