The Río Santa Lucía is a river in Corrientes Province, Argentina, flowing approximately 310 kilometers in total, of which around 190 kilometers constitute a defined channel. It originates in the Iberá Wetlands, where its headwaters emerge from low-gradient depressions and shallow marshes known locally as esteros. From there it flows predominantly from northeast to southwest, passing through nine departments — General Paz, San Miguel, Mburucuyá, Concepción, Saladas, San Roque, Bella Vista, Lavalle, and Goya — before emptying into the Río Paraná between the towns of Lavalle and Goya. The source elevation is approximately 63 meters, dropping to around 38 meters at the mouth.

The river drains a flat plains landscape, and its origins in the esteros mean that those wetlands act as natural buffers, significantly slowing drainage and dampening flood peaks. The drainage network has a rectangular pattern, with a well-defined, relatively straight main channel and tributaries joining at roughly right angles. This geometry, combined with the low-gradient terrain, creates generally calm, slow-moving water along much of the defined channel reach.

The town of Santa Lucía, which the river passes through and shares its name with, has a balneario (river beach) on its banks featuring white sand, a freshwater pool with continuous flow, and full visitor services. Kayaking and river excursions take place on the river in this area.

The river's connection to the Iberá Wetlands gives it ecological significance within the broader Corrientes river system, and the surrounding landscape reflects the characteristic flat, wetland-influenced geography of northeastern Argentina.