Saarlouis is a town in Saarland, Germany, capital of the district of Saarlouis. In 2020, the town had a population of 34,409. Saarlouis is located on the river Saar. It was built as a fortress in 1680 and was named after Louis XIV of France.

The Treaty of Paris of 1815, also known as the Second Treaty of Paris, was signed on 20 November 1815, after the defeat and the second abdication of Napoleon Bonaparte. In February, Napoleon had escaped from his exile on Elba, entered Paris on 20 March and began the Hundred Days of his restored rule. After France's defeat at the hands of the Seventh Coalition at the Battle of Waterloo, Napoleon was persuaded to abdicate again, on 22 June. King Louis XVIII, who had fled the country when Napoleon arrived in Paris, took the throne for a second time on 8 July.