William IV. (William Henry), king of Great Britain and Ireland, fifth sovereign of the Hanoverian line, born in London, Aug. 21, 1765, died at Windsor, June 20,1837. He was the third son of George III., and entered the navy June 15, 1779, as midshipman, on board the Prince George, which, being attached to Admiral Rodney's fleet, took part in two actions against the Spaniards. He served again in the channel fleet and in the fleet sent in 1781 to relieve Gibraltar, and in 1782 arrived at New York in the Prince George. Subsequently he served in the West Indies, having been transferred to the Warwick. In June, 1785, he was made a lieutenant, and in April, 1786, post captain in command of the Pegasus, and served under Nelson in the West Indies. Having gone north without orders, he was punished oh his return to England by confinement within the limits of Plymouth garrison, and by being sent abroad again to the Halifax station and the West Indies. He returned to England early in 1789, was made duke of Clarence, and took his seat in the house of lords on June 8. An income of £12,000 was settled upon him by parliament. When war with Spain was threatened, the duke of Clarence was appointed to the command of the Valiant of 74 guns, and later was made rear admiral of the blue.

In 1801 he reached the rank of admiral of the fleet. In the house of peers he seldom spoke except upon naval affairs; but he opposed the abolition of the slave trade, supported the peace of Amiens, and also the renewal of war with France in 1803, and in 1811 protested against the regency bill. At the close of 1813 he commanded on the Dutch coast, supporting Sir Thomas Graham against the French, and was slightly wounded. In 1818 he married the princess Adelaide of Saxe-Meiningen. On the trial of Queen Caroline he supported the king, and was severely handled by the queen's counsel. The death of the duke of York in 1827 made the duke of Clarence heir presumptive, and the Canning ministry revived for him the office of lord high admiral, which he held till September, 1828, although without a seat in the cabinet. He was foremost among the supporters of Catholic emancipation. On June 26,1830, he became king, a month before the French revolution. In England the tories were overthrown, and the whigs under Lord Grey came into power, pledged to parliamentary reform. After a severe struggle the reform bill received the royal assent, June 7, 1832, and soon after the West India slaves were emancipated.

The Grey ministry came to an end in 1834, when Lord Melbourne, also a whig, became premier; but the latter was dismissed the same year, the king having become alarmed by the political aspect, and being also strengthened by a conservative reaction. The new ministry, under Sir Robert Peel, was unable to maintain itself, and after a few months the Melbourne administration was restored. Reforms were made in the Irish church, the English municipal reform bill was passed, and relief was granted to the dissenters. William was about to change ministers again when he died. Having no legitimate issue, he was succeeded by his brother the duke of Cumberland in Hanover, and by his niece Victoria in Great Britain. By his mistress Mrs. Jordan he had five sons and five daughters, who were known by the name of Fitz-Clarence. The eldest was created earl of Munster, and was a major general in the army; the other sons held high positions, and the daughters all married among the aristocracy.