George III of the United Kingdom

George III secured passage of the Royal Marriages Act, requiring descendants of George II to obtain the monarch's consent before marrying. This aimed to prevent unsuitable marriages but caused future dynastic tensions.

George III's government attempted to suppress the American rebellion through military force. The war lasted eight years, ending with British defeat at Yorktown in 1781 and recognition of American independence in 1783.

The Treaty of Paris formally ended the American Revolutionary War, with Britain recognizing the United States as independent. This marked the end of the First British Empire and prompted imperial reorganization.

George III experienced his first major episode of what is now believed to be porphyria, causing temporary insanity. The Regency Crisis of 1788-89 ensued, with Parliament debating a regency under the Prince of Wales before the king recovered.

George III approved the Acts of Union that united Great Britain and Ireland into the United Kingdom of Great Britain and Ireland, effective January 1, 1801. The union was partly a response to the Irish Rebellion of 1798.

George III suffered a final, permanent relapse of his mental illness. The Regency Act 1811 appointed his eldest son, the Prince of Wales, as Prince Regent, effectively ending George III's active reign.