The Rímac River is located in western Peru and is the most important source of potable water for the Lima and Callao Metropolitan Area. It belongs to the Pacific Slope, into which it flows after bathing the cities of Lima and Callao, together with the Chillón River, to the north, and the Lurín River, to the south. It is 204 km long and has a basin of 3,312 km², of which 2,237.2 km² is a humid basin. The basin has a total of 191 lagoons, of which only 89 have been studied. The river begins in the highlands of the Huarochirí Province in the Lima Region and its mouth is located in Callao, near Jorge Chávez International Airport.

Lima, founded in 1535 as the Ciudad de los Reyes, is the capital and largest city of Peru. It is located in the valleys of the Chillón, Rímac and Lurín Rivers, in the desert zone of the central coastal part of the country, overlooking the Pacific Ocean. The city is considered the political, cultural, financial and commercial center of Peru. Due to its geostrategic importance, the Globalization and World Cities Research Network has categorized it as a "beta" tier city. Jurisdictionally, the metropolis extends mainly within the province of Lima and in a smaller portion, to the west, within the Constitutional Province of Callao, where the seaport and the Jorge Chávez Airport are located. Both provinces have regional autonomy since 2002.