The War of the Oranges (; ; ) was a brief conflict in 1801 in which France and Spain fought against Portugal, and was considered a precedent of the Peninsular War. The aftermath of the war resulted in Spanish control of the town of Olivenza (Olivença in Portuguese).

In 1800, Napoleon Bonaparte and his ally, Spanish minister Manuel de Godoy, ultimatively demanded Portugal, British ally since the Anglo-Portuguese Treaty of 1373, to enter into an alliance with France in the war against Britain and to cede to France the major part of its national territory.

Portugal refused, and in April 1801 French troops arrived in Portugal. On May 20, they were bolstered by Spanish troops under the command of Manuel de Godoy. In a battle that was disastrous for Portugal, Godoy took the Portuguese town of Olivença (Olivenza in Spanish), near the Spanish frontier. Following his victory, Godoy picked oranges at nearby Elvas and sent them to the Queen of Spain with the message that he would proceed to Lisbon. Thus, the conflict became known as the War of the Oranges.

On June 6, 1801, after Olivença, Portugal agreed to the tenets of the Treaty of Badajoz. On September 29, 1801, Portugal agreed to both maintaining the tenets of the Treaty of Badajoz and the alterations made to it, which were all embodied within the Treaty of Madrid.

After the Battle of Trafalgar in 1805, in which the Franco-Spanish fleet lost to Britain, the government of Portugal restored relations with its old ally. This led to the Peninsular War, in which France declared the Peace of Badajoz treaty cancelled, again marching on Portugal from 1807 to 1810.