Banda Oriental (Eastern Bank), or more fully Banda Oriental del Río Uruguay, was the name of the South American territories east of the Uruguay River and north of Río de la Plata that comprise the modern nation of Uruguay, the modern state of Rio Grande do Sul, Brazil, and part of the modern state of Santa Catarina, Brazil. It was the easternmost territory of the Viceroyalty of the Río de la Plata.
After decades of disputes over the territories, the 1777 First Treaty of San Ildefonso settled the division between the Spanish Empire and the Portuguese Empire: the southern part was to be held by the Spanish Viceroyalty of the Río de la Plata and the northern territories by the Portuguese Capitania de São Pedro do Rio Grande do Sul ().
The Banda Oriental was not a separate administrative unit until the de facto creation of the Provincia Oriental () by José Gervasio Artigas in 1813 and the subsequent decree of the Supreme Director of the United Provinces of the Río de la Plata of 7 March 1814, which formally established the Gobernación Intendencia Oriental del Río de la Plata (), making it a constituent part of the United Provinces of South America.
Indigenous tribes and the 16th century
thumb|Map of 1574 showing the Portuguese Captaincies
Before the arrival of the Spanish and the Portuguese, several tribes of indigenous people were living in this area as nomads. The principal ones were the Charrúas, the Chanás, the Guayanas and the Guaraníes. Juan Díaz de Solís discovered this territory in 1516. During the conquest of the Río de la Plata area by the "Adelantados" (1535–1590), the main concern was to reach the interior in search of precious metals, so this region remained mostly ignored. The first ephemeral Spanish attempts to start populated centres in this territory happened between 1527 and 1577. These were the Fortín de San Lázaro (actual Carmelo) and the Puerto de San Salvador (1527–1530) by Sebastián Gaboto, the Real de San Juan (1542–1553) and the Real de San Gabriel y Ciudad de San Salvador (1573–1577) by Juan Ortiz de Zárate.
In 1542 the Crown of Castile established the Viceroyalty of Peru, a colonial administrative district that originally contained most of Spanish-ruled South America, governed from the capital of Lima. The Banda Oriental was therefore officially under the administration of the Viceroyalty of Peru from 1542 up to 1776. Although the Treaty of Tordesillas (1494) limited the Portuguese colonies to the east of the 46th meridian, in practice, the Portuguese were free to advance in most of the territory that was not colonized by the Spanish, which included most of the Banda Oriental.
17th century
In the early 17th century the territory was called Banda Charrúa, later Otra Banda ("other shore"), and then Banda Oriental. Later the name was extended to encompass Entre Ríos, to describe the territories in those latitudes that lead to the Mar del Nord (Atlantic Ocean). The area north of the Banda Oriental was the territory called by the Guaraní word Mbiaza or Ibiazá, rendered in Spanish as La Vera.
thumb|left|Monument to Hernandarias in Montevideo
In 1618, during the governance of Hernando Arias de Saavedra (commonly known as Hernandarias), the Banda Oriental was integrated into the Spanish colonial Governorate of the Río de la Plata. Following the recommendation of the King of Spain, Hernandarias introduced a large amount of cattle in the Banda Oriental, an act which has played a decisive role in the future of the economy of the area. Starting around 1626, fathers of the Franciscan order attempted to establish reductions south of Río Negro. Some of them were short-lived missions like the San Francisco de los Olivares de los Charrúas, the San Antonio de los Chanáes and the San Juan de Céspedes. In contrast, the one of Santo Domingo Soriano, founded with Charrúas and Chanáes in Entre Ríos, Argentina, in 1664, was moved on the Isle of Vizcaíno, on the mouth of Río Negro and then in 1718 it was moved again at its present location in the modern Soriano Department.