It gives name to Guayas Province and is the most important river in South America that does not flow into the Atlantic Ocean or any of its marginal seas.

Its most important feature is the existence of a slough called Estero Salado, surrounded by swamps and affected by tides.

The Guayas River has the largest watershed in South America west of the Andes Mountains that flows into the Pacific Ocean.

It has an area 34,500 km2, in nine provinces: Los Ríos, Guayas, Bolívar, Manabí, Cañar, Pichincha, Azuay, Chimborazo and Cotopaxi.

In collaboration with the Estero Salado, the river discharges 36 billion cubic meters of water into the Gulf of Guayaquil every year.