Humedal Caleta Olivia, Natural wetland reserve in Caleta Olivia, Argentina.

Humedal Caleta Olivia, also called Segunda Laguna, is a saltwater wetland in the urban centre of Caleta Olivia, Santa Cruz. It lies between the Autovía Caleta Olivia and Avenida Las Flores, fed by rainwater from the surrounding hills and by groundwater. It is one of two wetlands within the city and is bordered by the Repsol-YPF oil pipeline to the north.

The wetland was declared a Provincial and Municipal Natural Reserve under Law No. 2563 (786), with boundaries set by Municipal Ordinance 308/38 of the year 2000. It is one of two wetlands in the urban centre of Caleta Olivia. In 2011, 58 adult flamingos and 2 chicks were counted; by June 2012, about 200 adults and 20 chicks had arrived, but they fled when earthworks for the Rotary XXIII ring road began.

Biology students from Escuela EBIMAL and the Instituto Aónikenk took up the lagoon's recovery as a school project, and a municipal environmental adviser called their proposals "very good". The Subsecretaría de Gestión Ambiental now runs awareness work among residents, treating a better "ecological culture" as a priority. Flamingos draw onlookers, but people have been seen killing the birds and dumping rubbish at the water's edge.

Access is available through marked paths near the coastal highway. Early morning provides the best conditions for observing birds, when most species are most active.

The wetland is fed by rainwater running down from the surrounding hills, and its surface has grown in recent months from groundwater input. Excess water passes to Primera Laguna and back through large pipes built by the municipality that act as communicating vessels.