Bernardo O'Higgins National Park is the largest of the protected areas in Chile, covering an area of 35,259.01 km². The park is named after General Bernardo O'Higgins, first head of state of the Republic of Chile. Los Glaciares National Park (Argentina) and Torres del Paine National Park are its neighbours to the east, Laguna San Rafael National Park is located to the north, the Alacalufes National Reserve to the southwest and the Katalalixar National Reserve to the northwest.
The park includes a great part of the Southern Patagonian Ice Field. One of its main attractions is the glacier Pío XI, from which enormous ice blocks periodically spall. The Pío XI glacier is the largest glacier of the South hemisphere outside of Antarctica, covering an area of 1,265 km², advancing over the past 50 years by more than 10 kilometers; one of its tongues measures approximately 6 kilometers.