Queen Victoria surpasses her grandfather King George III as the longest reigning monarch in British history.

George III (George William Frederick; 4 June 1738 29 January 1820) was King of Great Britain and of Ireland from 25 October 1760 until the union of the two kingdoms on 1 January 1801, after which he was King of the United Kingdom of Great Britain and Ireland until his death in 1820. He was the longest-lived and longest-reigning king in British history. He was concurrently Duke and Prince-elector of Brunswick-Lneburg ("Hanover") in the Holy Roman Empire before becoming King of Hanover on 12 October 1814. He was a monarch of the House of Hanover but, unlike his two predecessors, he was born in Great Britain, spoke English as his first language and never visited Hanover.George's life and reign were marked by a series of military conflicts involving his kingdoms, much of the rest of Europe, and places farther afield in Africa, the Americas and Asia. Early in his reign, Great Britain defeated France in the Seven Years' War, becoming the dominant European power in North America and India. However, many of Britain's American colonies were soon lost in the American War of Independence. Further wars against revolutionary and Napoleonic France from 1793 concluded in the defeat of Napoleon at the Battle of Waterloo in 1815. In 1807, the transatlantic slave trade was banned from the British Empire.

In the later part of his life, George had recurrent, and eventually permanent, mental illness. Although it has since been suggested that he had bipolar disorder or the blood disease porphyria, the cause of his illness remains unknown. George suffered a final relapse in 1810, and his eldest son, the Prince of Wales, became Prince Regent the following year. When George III died in 1820, the Regent succeeded him as King George IV. Historical analysis of George III's life has gone through a "kaleidoscope of changing views" that have depended heavily on the prejudices of his biographers and the sources available to them.

Victoria (Alexandrina Victoria; 24 May 1819 – 22 January 1901) was Queen of the United Kingdom of Great Britain and Ireland from 20 June 1837 until her death in 1901. Known as the Victorian era, her reign of 63 years and seven months was longer than any previous British monarch. It was a period of industrial, political, scientific, and military change within the United Kingdom, and was marked by a great expansion of the British Empire. In 1876, the British Parliament voted to grant her the additional title of Empress of India.

Victoria was the daughter of Prince Edward, Duke of Kent and Strathearn (the fourth son of King George III), and Princess Victoria of Saxe-Coburg-Saalfeld. After the deaths of her father and grandfather in 1820, she was raised under close supervision by her mother and her comptroller, John Conroy. She inherited the throne aged 18 after her father's three elder brothers died without surviving legitimate issue. Though a constitutional monarch, Victoria privately attempted to influence government policy and ministerial appointments; publicly, she became a national icon who was identified with strict standards of personal morality.

Victoria married her first cousin Prince Albert of Saxe-Coburg and Gotha in 1840. Their children married into royal and noble families across the continent, earning Victoria the sobriquet "the grandmother of Europe" and spreading haemophilia in European royalty. After Albert's death in 1861, Victoria plunged into deep mourning and avoided public appearances. As a result of her seclusion, British republicanism temporarily gained strength, but in the latter half of her reign, her popularity recovered. Her Golden and Diamond Jubilees were times of public celebration. She died on the Isle of Wight in 1901. The last British monarch of the House of Hanover, she was succeeded by her son Edward VII of the House of Saxe-Coburg and Gotha.