The Battle of Mataquito was fought in the Arauco War on April 30, 1557, between the Spanish forces of the governor, Francisco de Villagra, and Mapuche headed by their toqui Lautaro. It was a dawn surprise attack on Lautaro's fortified camp between a wooded mountain and the shore of the Mataquito River. The battle is notable for ending Mapuche pretensions to expulse the Spanish from Santiago, while also avenging the death of former governor Pedro de Valdivia who had been killed by Lautaro's warriors four years earlier.

The Mapuche ( (Mapuche & Spanish: [maˈputʃe])) are a group of Indigenous inhabitants of present-day south-central Chile and southwestern Argentina, including parts of present-day Patagonia. The collective term refers to a wide-ranging ethnicity composed of various groups who shared a common social, religious, and economic structure, as well as a common linguistic heritage as Mapudungun speakers. Their influence once extended from Aconcagua Valley to Chiloé Archipelago and later spread eastward to Puelmapu, a land comprising part of the Argentine pampa and Patagonia. Today the collective group makes up over 80% of the indigenous peoples in Chile, and about 9% of the total Chilean population. The Mapuche are particularly concentrated in the Araucanía region. Many have migrated from rural areas to the cities of Santiago and Buenos Aires for economic opportunities.

The Mapuche traditional economy is based on agriculture; their traditional social organization consists of extended families, under the direction of a lonko or chief. In times of war, the Mapuche would unite in larger groupings and elect a toki (meaning "axe" or "axe-bearer") to lead them. Mapuche material culture is known for its textiles and silverwork.

At the time of Spanish arrival, the Araucanian Mapuche inhabited the valleys between the Itata and Toltén rivers. South of there, the Huilliche and the Cunco lived as far south as the Chiloé Archipelago. In the seventeenth, eighteenth and nineteenth centuries, Mapuche groups migrated eastward into the Andes and pampas, fusing and establishing relationships with the Poya and Pehuenche. At about the same time, ethnic groups of the pampa regions, the Puelche, Ranquel and northern Aonikenk, made contact with Mapuche groups. The Tehuelche adopted the Mapuche language and some of their culture, in what came to be called Araucanization, during which Patagonia came under effective Mapuche suzerainty.

Mapuche in the Spanish-ruled areas, especially the Picunche, mingled with Spanish during the colonial period, forming a mestizo population that lost its indigenous identity. But Mapuche society in Araucanía and Patagonia remained independent until the late nineteenth century, when Chile occupied Araucanía and Argentina conquered Puelmapu. Since then the Mapuche have become subjects, and then nationals and citizens of the respective states. Today, many Mapuche and Mapuche communities are engaged in the so-called Mapuche conflict over land and indigenous rights in both Argentina and in Chile.