He was the third son of Henry Fox, 1st Baron Holland, one of the older generation self-aggrandizing Whigs. His mother was Lady Caroline Lennox, daughter of the Duke of Richmond. Fox was educated at Eton and Hertford College, Oxford. He was over indulged by his father and quickly entered into an extravagant and dissolute lifestyle, in 1774 he was £140,000 in debt. Fox became MP for Midhurst in 1768, although he was legally too young. He supported Grafton and his attacks on the radical John Wilkes. Fox was made a junior lord of the Admiralty by North in 1770, he resigned in January 1772 in order to vote against the Royal Marriage Act but was reappointed to a government post at the Treasury in December but was finally dismissed by North in February 1774, following pressure from George III.
Out of government Fox became more radical, progressing from his friendship of Edmund Burke to becoming a leader of the Rockinghamite Whigs. Fox won the seat of Westminster in 1781 and showed his support for Parliamentary reform. When Rockingham became Prime Minister in 1782 Fox was made the first foreign secretary. When Rockingham died (July 1, 1782) Fox unwisely resigned over the appointment of Shelburne as Prime Minister. In February 1783 Fox formed an alliance of convenience with North to regain power.
Fox and North came to power in April 1783 over the king's resistance, although Portland actually headed the government the two men were both secretaries of state. The ambitions of both Fox and North were blunted by the active efforts of the king and they angered him further with their open support of the Prince Regent. They were both driven from office by the efforts of the king's supporters following the failure of Fox's East India Bill in December. The March 1784 election was a sad defeat for the opposition although Fox was re-elected.
He remained a force in the Whigs and his support of the French Revolution (1789) led to a split in the Whigs between the supporters of the revolution and the others who joined William Pitt the Younger, leaving the opposition as no more than sixty MPs. Fox had become convinced that the king and the establishment were more of a threat to the constitution than 'radical' politics and protested against the curtailment of liberties associated with the war against France. In 1792 Fox saw through the only piece of substantial legislation in his career, the Libel Act, which restored to juries the right to decide what was libel and whether a defendant was guilty. Fox married his mistress, Elizabeth Armistread, in 1795 but did not make this fact public until 1802.
Fox and much of the opposition deliberately withdrew from political life from 1797. He returned following the Treaty of Amiens and having assisted in the replacement of Henry Addington, when Pitt was succeeded by Grenville he was made foreign secretary in the "Ministry of all the Talents" and died in office. He was buried in Westminster Abbey.