Born George William Frederick, George III (1738-1820), King of Great Britain and Ireland (1760-1820) and King of Hanover (1760-1820), was the grandson and successor of George II. He was the third British monarch of the House of Hanover, and the first to be born in Britain and speak English as his first language. It was during George III's reign that Great Britain lost many of its colonies in North America in the wake of the American Revolution. These colonies would eventually become the United States. Also during his reign the realms of Great Britain and Ireland were joined together to form the United Kingdom.

Later in his reign George III suffered from recurrent and, eventually, permanent mental illness. This baffled medical science at the time, although it is now generally thought that he suffered from the blood disease porphyria. Recently, owing to studies showing high levels of the poison arsenic in King George's hair, arsenic is also thought to be a possible cause of King George's insanity and health problems. After a final relapse in 1810, George's eldest son, George, Prince of Wales ruled as Prince Regent. Upon George's death, the Prince of Wales succeeded his father as George IV. (From Wikipedia).