Catherine Sedley, Countess of Dorchester, Countess of Portmore (21 December 1657 – 26 October 1717), daughter of Sir Charles Sedley, 5th Baronet, was the mistress of King James II and VII both before and after he came to the throne. Catherine was noted not for beauty but for her celebrated wittiness and sharp tongue.
Catherine was the only legitimate child of the Restoration poet Sir Charles Sedley. Her mother was Lady Catherine Savage, daughter of John Savage, 2nd Earl Rivers. She grew up "notoriously plain" (brunette and thin rather than plump and fair). While her father roistered around England, her mother spiraled into insanity until she entered a psychiatric hospital in Ghent in Catherine's early teens. At this low point in her life, Sir Charles introduced a common-law wife, Anne Ayscough, into the family and ejected Catherine from the house.
She worked for Italian princess Mary of Modena, who had just married James, Duke of York, heir to the British throne. This eventually led to an affair with him. She was bewildered at having been chosen by James. "It cannot be my beauty for he must see I have none," she remarked incredulously. "And it cannot be my wit, for he has not enough to know that I have any." James in fact was often attracted to women who were generally considered plain, if not ugly; his brother Charles II once joked that his confessor must impose these mistresses on him as a penance.
After his accession James yielded to pressure from his confessor Fr. Bonaventure Giffard, backed by the Earl of Sunderland and several Catholic councillors, and put her away for a time. While James by his own account took Giffard's intervention "very kindly, he being a truly religious man" he told his councillors sharply "not to meddle in things that in no way related to them," adding, with a rare touch of humour, that he had not heard that they had all entered the priesthood too.