The Neapolitan War between the Napoleonic Kingdom of Naples and the Austrian Empire starts on March 15, 1815 when Joachim Murat declares war on Austria and ends on May 20, 1815 with the signing of the Treaty of Casalanza.

The war occurs during the Hundred Days between Napoleon's return from exile and before he leaves Paris to be decisively defeated at the Battle of Waterloo.

The war is triggered by a pro-Napoleon uprising in Naples, and ends after a decisive Austrian victory at the Battle of Tolentino and Ferdinand IV is reinstated as King of Naples and Sicily.

However, the intervention by Austria causes resentment in Italy, which further spurs on the drive towards Italian unification.