The Third Carlist War (Spanish: Tercera Guerra Carlista) (1872–1876) is the last Carlist War in Spain.

It is very often referred to as the Second Carlist War, as the 'second' (1847–49) had been small in scale and almost trivial in political consequence.During this conflict, Carlist forces manage to occupy several towns in the interior of Spain, the most important ones being La Seu d'Urgell and Estella in Navarre.

Isabel II is in exile, and King Amadeo I of Spain, crowned in 1871, is not very popular.The Carlist pretender, "Carlos VII", grandson of Carlos V tries to earn the support of those areas with more region-specific customs and former laws.

The Carlists proclaim the restoration of Catalonian, Valencian and Aragonese fueros (charters), abolished at the beginning of the 18th century by Philip V by means of the New Planning unilateral Royal decrees.However, the call for rebellion made by the Carlists is echoed in Catalonia and especially the Basque region (Gipuzkoa, Álava, Biscay and Navarre), where the Carlists manage to design a temporary state.

The Carlists manage to lay siege to Bilbao and San Sebastián, but fail to seize them.

After four years of war, on February 27, 1876, the Carlist pretender goes into exile in France.

On the same day, King Alfonso XII of Spain lands in Pamplona.After the end of the war, the Basque charters (fueros/foruak) are abolished, thereby shifting the border customs from the Ebro river to the coast and establishing the compulsory conscription in the Spanish army for the youth of the chartered territories.The war causes between 7,000 and 50,000 casualties.