The correct answer is option 3: 1815. Napoleon was finally overthrown in the Battle of Waterloo, which took place in the year 1815. The battle is widely regarded as one of the most significant events in European history, as it marked the end of Napoleon`s reign as Emperor of the French. The battle was fought on June 18, 1815, near the town of Waterloo in present-day Belgium. Napoleon faced a coalition of European powers led by the Duke of Wellington and Prussian Field Marshal Gebhard von Blücher. The French army was defeated, and Napoleon was subsequently forced to abdicate the throne and was exiled to the island of Saint Helena, where he died in 1821.