Avenida 18 de Julio, or 18 de Julio Avenue, is the most important avenue in Montevideo, Uruguay. It is named after the date when the country's first Constitution was sworn in, on July 18, 1830.

Montevideo is the capital and largest city of Uruguay. According to the 2011 census, the city proper has a population of 1,319,108 in an area of 201 square kilometers (78 sq mi). Montevideo is situated on the southern coast of the country, on the northeastern bank of the Río de la Plata.