1762–1830, king of Great Britain and Ireland (1820–30), eldest son and successor of George III. In 1785 he married Maria Anne Fitzherbert, a Roman Catholic. The marriage was illegal, however; and in 1795, to secure parliamentary settlement of his enormous debts, he made a political marriage with Caroline of Brunswick. In constant and open opposition to his father, George associated closely with the Whigs, particularly Charles James Fox, whose friend he became in 1781. As a result, when George III had his first serious fit of insanity in 1788–89, the Tory William Pitt proposed that the regency vested in the prince be closely restricted (to prevent George bringing his Whig friends to power), while Fox, usually the opponent of royal prerogative, wanted the prince to have unlimited powers as regent. In 1811, after the king had become permanently incapacitated, George became regent on terms very similar to those proposed by Pitt in 1788. However, when the limitations on his power to make appointments and spend crown revenues were removed in 1812, the prince regent retained most of his father's ministers, breaking his connection with the Whigs. The Tories, under the leadership of the 2d earl of Liverpool for most of the period, remained entrenched in power throughout the regency and George's subsequent reign. As regent and as king, George was hated for his extravagance and dissolute habits, and he aroused particular hostility by an unsuccessful attempt, immediately after his accession (1820) to the throne, to divorce his long-estranged wife, Caroline. During his reign the monarchy lost a significant amount of power. George's only legitimate child, Charlotte Augusta, married (1816) Prince Leopold of Saxe-Coburg (later Leopold I, king of the Belgians) but died in childbirth in 1817. George was succeeded by his brother William IV.

George was the eldest son of George III and Charlotte Sophia of Mecklenburg-Strelitz. In November 1810, George III became permanently insane, and shortly afterward the prince became regent under the terms of the Regency Act (1811). Succeeded to his father in 1820.

George IV's accession on the death of his father did not add to the powers that he had possessed as regent. He insulted and intrigued against the 2nd Earl of Liverpool, prime minister from 1820 to 1827. George Canning, who became foreign secretary in 1822 and prime minister in 1827, won George's approval. But after 1827 he ceased to have any personal weight with either of the two great parties.

George’s profligacy and marriage difficulties meant that he never regained much popularity, and he spent his final years in seclusion at Windsor, dying at the age of 67

As Prince of Wales he supported the Whig opposition party, enjoyed a succession of passionate love affairs and two marriages. In 1785 he secretly wed Catholic widow Maria Fitzherbert and in 1795 entered into a disastrous official union with Caroline of Brunswick. He became Prince Regent in 1811 when his father was thought to be mad, and was crowned in 1820. He died in 1830 leaving a rich art collection and an architectural legacy including Buckingham Palace, Windsor Castle and the Royal Pavilion.