Ernesto Tornquist Provincial Park, Natural reserve in Tornquist Partido, Argentina.

Ernesto Tornquist Provincial Park is a protected area spanning mountains, grasslands, and valleys across Buenos Aires province. The territory offers numerous hiking trails and viewing spots where visitors can explore different landscapes.

Ernesto Tornquist Provincial Park was established on 23 April 1958 as a provincial protected area in the Ventania System. It is named after Ernesto Tornquist, and its roughly 9,879 hectares lie along Provincial Route 76 at kilometre 225, in Tornquist Partido. The park protects the headwaters of the Sauce Grande, a water source for Bahía Blanca.

Rock paintings scattered throughout the park mark where indigenous hunter-gatherers once lived and worked in these mountains. Visitors walking the trails can spot these ancient marks on stone faces along the way.

The park can be explored from two main bases: one near Cerro Ventana and another near Cerro Bahia Blanca. Ranger stations at both locations provide guidance and local knowledge to help visitors navigate the area.

The park's botanical garden studies and protects endemic plants of the Ventania System, among them Polygala ventanensis and Mostacillastrum ventanense, whose populations consist of only a few grouped individuals. Outside park limits no specimens of these species have been found.