Uruguaiana is a city and municipality in the Brazilian state of Rio Grande do Sul. It is located on the eastern shore of the Uruguay River bordering Argentina. Opposite to Uruguaiana, and joined to it by a road/railway bridge, lies the Argentine city of Paso de los Libres, Corrientes. North of Uruguaiana lies the Brazilian municipality of Itaqui, connected by a bridge constructed by the British in 1888 over the Ibicuí River. The municipality also borders the municipalities of Alegrete, Barra do Quaraí and Quaraí, and, also, Uruguay, making it one of the few international triple-border municipalities of Brazil.

The city marks the southernmost point reached by the Paraguayans in the Paraguayan War; after being taken without resistance, it was recaptured after a six-week siege that effectively ended the phase of Paraguayan offensive operations.

Nowadays, Uruguaiana represents the biggest in population and arguably^{[unbalanced opinion?]} most important municipality of the sparsely populated western Rio Grande do Sul.

Uruguaiana is also home to the California da Canção Nativa.

The major highways connecting Uruguaiana with other cities in Rio Grande do Sul are BR 472, to Barra do Quaraí in the south and São Borja in the north, BR 290, to Alegrete and Porto Alegre in the east.

The city is served by Ruben Berta International Airport, the largest airport in the interior of the state. It had a traffic of over 3,000 passengers in 2008 with 1,409 planes using the facilities.

Some of the distances between Uruguaiana and other cities in the state are:

Uruguaiana has a humid subtropical climate (Köppen: Cfa) with hot summers and mild winters.