The War of the Third Coalition was a European conflict lasting from 1805 to 1806 and was the first conflict of the Napoleonic Wars. During the war, France and its client states under Napoleon I opposed an alliance, the Third Coalition, which was made up of the United Kingdom, the Austrian Empire, the Russian Empire, Naples, Sicily, and Sweden. Prussia remained neutral during the war.

Napoleon Bonaparte, later known by his regnal name Napoleon I, was a French emperor and military commander who rose to prominence during the French Revolution and led successful campaigns during the Revolutionary Wars. He was the leader of the French Republic as First Consul from 1799 to 1804, then of the French Empire as Emperor of the French from 1804 until 1814, and briefly again in 1815. His political and cultural legacy endures as a celebrated and controversial leader. He is considered one of the greatest military commanders in history and his wars and campaigns are still studied at military schools worldwide. However, historians still debate the degree to which he was responsible for the Napoleonic Wars, in which between three and six million people died. Napoleon brought modernizing reforms to France and Western Europe and stimulating the development of nation states. He also sold the Louisiana Territory to the United States in 1803, doubling the latter's size. However, his mixed record on civil rights and exploitation of conquered territories adversely affect his reputation.