William IV, King of Great Britain, 1765-1837

William IV was King of the United Kingdom of Great Britain and Ireland and King of Hanover. The third son of George III, William succeeded his elder brother George IV. He served in the Royal Navy in his youth, spending time in North America and the Caribbean, and was later nicknamed the "Sailor King". In 1789, he was created Duke of Clarence and St Andrews. In 1827, he was appointed as Britain's first Lord High Admiral since 1709. As his two older brothers died without leaving legitimate issue, he inherited the throne when he was 64 years old. His reign saw several reforms: the poor law was updated, child labour restricted, slavery abolished in nearly all of the British Empire, and the British electoral system refashioned by the Reform Act 1832.

At the time of his death, William had no surviving legitimate children. Late in life, he married Queen Adelaide. William was succeeded by his niece Queen Victoria in the United Kingdom, and his brother King Ernest Augustus in Hanover.