George III (George William Frederick; 4 June 1738 – 29 January 1820) was King of Great Britain and Ireland from 25 October 1760 until his death in 1820. He was concurrently duke and prince-elector of Hanover in the Holy Roman Empire before becoming King of Hanover on 12 October 1814. He was the first monarch of the House of Hanover who was born in Great Britain, spoke English as his first language, and never visited Hanover. George was born during the reign of his paternal grandfather, King George II, as the first son of Frederick, Prince of Wales, and Princess Augusta of Saxe-Gotha. Following his father's death in 1751, Prince George became heir apparent and Prince of Wales. He succeeded to the throne on George II's death in 1760. The following year, he married Princess Charlotte of Mecklenburg-Strelitz, with whom he had 15 children. George III'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, Britain lost 13 of its North American colonies 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. The Acts of Union 1800 merged the separate kingdoms of Great Britain and Ireland into the United Kingdom of Great Britain and Ireland. 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. The exact nature of George's illness is not known definitively, but historians and medical experts have suggested that his symptoms and behaviour traits were consistent with either bipolar disorder or porphyria. In 1810, George suffered a final relapse, and his eldest son, George, Prince of Wales, was named Prince Regent the following year. The King died aged 81, at which time the Regent succeeded him as George IV. George III reigned during much of the Georgian and Regency eras. At the time of his death, he was the longest-lived and longest-reigning British monarch, having reigned for 59 years and 96 days; he remains the longest-lived and longest-reigning male monarch in British history.