George IV, King /ˌdʒɔːdʒ ðə ˈfɔːθ $ ˌdʒɔːrdʒ ðə ˈfɔːrθ/ BrE AmE
(1762–1830) the king of Great Britain and Ireland from 1820 until his death. From 1811 to 1820, he acted as king and had the title ‘Prince Regent’, because his father, King George III, was mentally ill and unable to rule. This period of British history is called ‘the Regency’.