Guerrilla warfare in the Peninsular War refers to the armed civilian actions carried out by non-regular troops against Napoleon's Grande Armée in Spain and Portugal during the Peninsular War.

The Dutch Brigade was a unit of the Royal Army of the Kingdom of Holland. King Louis Bonaparte sent the brigade in September 1808, to take part in the Peninsular War on the French side at the request of his brother Emperor Napoleon of France. The brigade was under the command of Major-General David Hendrik Chassé and was made part of the so-called "German Division". The Division also consisted of units from the Nassau, the Baden and other German allies of the French empire commanded by the French general Leval. It was, in turn, part of the IVth French Corps commanded by Marshals Lefebvre and Sébastiani, and was later part of the Marshal Victor's Ist Corps. The brigade distinguished itself initially in several major battles, and was later employed mainly in counter-guerrilla warfare. After the annexation of the Kingdom of Holland by the French empire in 1810, the brigade was formally decommissioned and its members, now French subjects, absorbed into the French 123rd Line Infantry Regiment, and later into the 130th Line Infantry Regiment. The other battalions of the 123rd remained in the Netherlands and were later reassigned to the Russian campaign of 1812.