The siege of Badajoz, also called the third siege of Badajoz, was an Anglo-Portuguese Army under the Earl of Wellington besieged Badajoz, Spain, and forced the surrender of the French garrison. The siege was one of the bloodiest in the Napoleonic Wars and was considered a costly victory by the British, with some 4,800 Allied soldiers killed or wounded in a few short hours of intense fighting during the storming of the breaches as the siege drew to an end. Enraged at the huge number of casualties they suffered in seizing the city, the troops broke into houses and stores consuming vast quantities of alcohol with many of them then going on a rampage, threatening their officers and ignoring their commands to desist, and even killing several. It took three days before the men were brought back into order. When order was restored, an estimated 200–300 civilians had been killed or injured.

The Anglo-Portuguese Army was the combined British and Portuguese army that participated in the Peninsular War, under the command of Arthur Wellesley. The Army is also referred to as the British-Portuguese Army and, in Portuguese, as the Exército Anglo-Luso or the Exército Anglo-Português.