Isabella Ingram-Seymour-Conway, Marchioness of Hertford

Isabella Anne Seymour-Conway, Marchioness of Hertford (7 July 1759 – 12 April 1834) was an English landowner and courtier and a mistress of King George IV when he was Prince of Wales. She was born at Temple Newsam in Leeds, and was the eldest daughter of Charles Ingram, 9th Viscount of Irvine, and his wife Frances Gibson Shepheard Ingram. She married Francis Ingram-Seymour-Conway, 2nd Marquess of Hertford, in 1776, at age sixteen, being his second wife. she caught the attention of the Prince of Wales most likely at a ball or concert at Manchester House, the London home of the Hertfords. Isabella was criticised by the House of Lords and in the press for her influence on George; satirical prints by George Cruikshank and others were produced.

The Marchioness's predecessor as the Prince Regent's mistress had been Maria Fitzherbert, a Roman Catholic. Other Catholics disapproved of the Marchioness's influence over the prince, referring to "the fatal witchery of an unworthy secret influence" that they felt had turned him against the idea of Catholic emancipation. George Canning, speaking for the party in power, made use of these comments to say that, if Lady Hertford was really responsible for the prince's political decisions, she was "Britain's guardian angel". Isabella made a point of humiliating Mrs Fitzherbert and by 1811 the Prince had formally separated from her. She and her husband added the name of Ingram to their surname due to the fortune they inherited from her family.

Isabella continued to spend the season in London, but otherwise lived at Temple Newsam. Here she busied herself with charitable works, being the patron or member of many events and societies, and was noted for her benevolence to the poor as well as her generosity to the servants at Temple Newsam who held an annual ball and supper in the house. Lady Hertford died in 1834 after catching a cold on her way from Temple Newsam to London by carriage. Her obituary in The Leeds Intelligencer described her as 'Her intellectual character, and high attainments, formed the least part of her excellencies; however enlightened her mind, her heart was warmer still. To the poor and the distressed her munificence was all but unbounded'.