George was born in London at Norfolk House. He was the grandson of King George II, and the eldest son of Frederick, Prince of Wales, and Augusta of Saxe-Gotha. As Prince George was born two months prematurely and he was thought unlikely to survive, he was baptised the same day by Thomas Secker, who was both Rector of St James's and Bishop of Oxford. One month later, he was publicly baptised at Norfolk House, again by Secker. His godparents were the King of Sweden (for whom Lord Baltimore stood proxy), his uncle the Duke of Saxe-Gotha (for whom Lord Carnarvon stood proxy) and his great-aunt the Queen of Prussia (for whom Lady Charlotte Edwin stood proxy).
George grew into a healthy but reserved and shy child. The family moved to Leicester Square, where George and his younger brother Prince Edward, Duke of York and Albany, were educated together by private tutors. Family letters show that he could read and write in both English and German, as well as comment on political events of the time, by the age of eight.
He was the first British monarch to study science systematically. Apart from chemistry and physics, his lessons included astronomy, mathematics, French, Latin, history, music, geography, commerce, agriculture and constitutional law, along with sporting and social accomplishments such as dancing, fencing, and riding. His religious education was wholly Anglican. At age 10 George took part in a family production of Joseph Addison's play Cato and said in the new prologue: "What, tho' a boy! It may with truth be said, A boy in England born, in England bred". Historian Romney Sedgwick argued that these lines appear "to be the source of the only historical phrase with which he is associated".
George's grandfather, King George II, disliked the Prince of Wales, and took little interest in his grandchildren. However, in 1751 the Prince of Wales died unexpectedly from a lung injury, and George became heir apparent to the throne. He inherited one of his father's titles and became the Duke of Edinburgh. Now more interested in his grandson, three weeks later the King created George Prince of Wales (the title is not automatically acquired).
In the spring of 1756, as George approached his eighteenth birthday, the King offered him a grand establishment at St James's Palace, but George refused the offer, guided by his mother and her confidant, Lord Bute, who would later serve as Prime Minister. George's mother, now the Dowager Princess of Wales, preferred to keep George at home where she could imbue him with her strict moral values.
In late 1810, at the height of his popularity, already virtually blind with cataracts and in pain from rheumatism, George became dangerously ill. In his view the malady had been triggered by stress over the death of his youngest and favourite daughter, Princess Amelia. The Princess's nurse reported that "the scenes of distress and crying every day ... were melancholy beyond description." He accepted the need for the Regency Act of 1811, and the Prince of Wales acted as Regent for the remainder of George III's life. Despite signs of a recovery in May 1811, by the end of the year George had become permanently insane and lived in seclusion at Windsor Castle until his death.
Prime Minister Spencer Perceval was assassinated in 1812 and was replaced by Lord Liverpool. Liverpool oversaw British victory in the Napoleonic Wars. The subsequent Congress of Vienna led to significant territorial gains for Hanover, which was upgraded from an electorate to a kingdom.
Meanwhile, George's health deteriorated. He developed dementia, and became completely blind and increasingly deaf. He was incapable of knowing or understanding either that he was declared King of Hanover in 1814, or that his wife died in 1818. At Christmas 1819, he spoke nonsense for 58 hours, and for the last few weeks of his life was unable to walk.