George III was born in 1738, first son of Frederick, Prince of Wales and Augusta. He married Charlotte of Mecklenburg-Strelitz in 1761, to whom he was devoted. The couple produced a prolific fifteen children: nine sons and six daughters. George was afflicted with porphyria, a maddening disease which disrupted his reign as early as 1765. Several attacks strained his grip on reality and debilitated him in the last years of his reign. Personal rule was given to his son George, the Prince Regent, in 1811. George III died blind, deaf and mad at Windsor Castle on January 29, 1820.

George III succeeded his grandfather, George II, in 1760 (Frederick, Prince of Wales, had died in 1751 having never ruled). George was determined to recover the prerogative lost to the ministerial council by the first two Georges; in the first two decades of the reign, he methodically weakened the Whig party through bribery, coercion and patronage. Prime Minister, William Pitt the Elder was toppled by Whigs after the Peace of Paris, and men of mediocre talent and servile minds were hand-picked by George as Cabinet members, acting as little more than yes-men. Bouts with madness and the way he handled the American Revolution eroded his support and the power of the Crown was granted again to the Prime Minister.

The Peace of Paris (1763) ended the Seven Years' War with France, with the strenuous, anti-French policies of the elder Pitt emphasizing naval superiority in the colonial warfare. Great Britain emerged from the conflict as the world's greatest colonial power. England thrived under peacetime conditions, but George's commitment to taxing the American colonies to pay for military protection led to hostilities in 1775. The colonists proclaimed independence in 1776, but George obstinately continued the war until the final American victory at Yorktown in 1781. The Peace of Versailles, signed in 1783, ensured British acknowledgment of the United States of America. The defeat cost George dearly: his sanity was stretched to the breaking point and his political power decreased when William Pitt the Younger became Prime Minister in 1783. George reclaimed some of his power, driving Pitt from office from 1801-04, but his condition worsened again and he ceased to rule in 1811.

The peace following the French war settlement was short-lived. A mere ten years later, England joined a continental alliance against French revolutionary forces who, after gaining power in France, sought total French hegemony across Europe. By 1797, the largest part of Europe was under French dominance, with England standing alone against the revolutionary Republic. The British Navy again proved decisive, defeating French forces at Camperdown, Cape St. Vincent and the Battle of the Nile in 1797, and finally at Copenhagen in 1801. Peace was negotiated at Amiens in 1802, with the French supreme on land and the British at sea. Napoleon Bonaparte seized supreme power in France at the turn of the century, and renewed attacks against England in 1803. Hostilities with France lasted until 1814 taking several forms. Arthur Wellesley, Duke of Wellington, led the land attack; the navy, commanded by Lord Horatio Nelson won the decisive battle off Cape Trafalgar, and imposed a blockade of Europe to offset Napoleon's "continental system" which was forbidden from importing British goods; and the younger Pitt guided the government through the hardships of total war. In addition to the continental conflict, England went to war again with the United States between 1812-14, over the British practice of pressing American seamen into service in the British Navy. Both conflicts were resolved in 1814; Napoleon was deposed and England agreed not to abscond with American sailors. Napoleon returned to Europe briefly in 1815, but was soundly defeated by continental forces led by Wellington.

Other events and people also marked the reign. A second Act of Union was passed in 1801, bringing Ireland under the umbrella of Great Britain until the Government of Ireland Act (1920) established the modern arrangement. Slave trade was abolished in 1807, although slavery continued in British colonies until 1833. Population increases, improvements in agricultural and industrial methods and a revolution in transportation spurred British economic growth. English literature was graced by some of its best known authors: Wordsworth, Shelley and Keats were among the writers of the era.

George's madness ultimately left the fate of the crown on his eldest son George, Prince Regent. Prince George was put in the daunting position of attempting to govern according to the increasingly erratic will of his father. A letter received by novelist E. M. Frostier from his aunt, Marine Thornton, describes the situation:

"... there he was sitting on the Throne with his King's Crown on, his robes scarlet and ermine, and held his speech written out for him, just what he had to say. But, oh dear, he strode up and made a bow and began 'My Lords and Peacocks.' The people who were not fond of him laughed, the people who did love him cried, and he went back to be no longer a king, and his eldest son reigned in his stead."