Frances, the wife of the famous Lord Sussex, whom Sir Walter Scott has described in absurdly complimentary terms in Kenilworth, was the youngest daughter of Sir William Sidney, by his wife Anne, daughter of Sir Hugh Pagenham, and widow of Thomas Fitzwilliam, brother of Lord Southampton. She was thus sister to Sir Henry Sidney, who succeeded her husband as Lord Deputy in Ireland, and of whom Lord Sussex ever after remained unduly jealous, notwithstanding all the efforts of his wife towards a reconciliation.

Married to Thomas Radcliffe, Earl of Sussex, April 26, 1555, Frances was left a widow in June, 1583. In March, 1589, she died at Bermondsey, and was buried in St. Paul's Chapel, Westminster Abbey.

Throughout her married life and widowhood Lady Sussex had been noted for her boundless benevolence and her support of the new-born Anglican Church, of whose communion she was a staunch member. Lord Sussex having no children by her, she bequeathed nine-tenths of her property to charity. It is to the last will and testament of this munificent and noble lady that Cambridge University owes the institution of that celebrated college which bears her maiden name, coupled with the title of her husband.

By this will she bequeathed the sum of £5,000, as well as other additional property, for the foundation and endowment at Cambridge of a college to be christened the "Lady Frances Sidney-Sussex." Should this sum and the attendant property prove insufficient for the purpose of erecting such a College, it was to be expended instead in adorning, enriching, and enlarging Clare Hall, on condition that this institution should, out of grateful remembrance, be known in future as the "Clare and Lady Frances Sidney-Sussex College." The foundation of the new college took place in 1596, and it was formally opened on its completion, some three years later.