San Alfonso del Mar is a private resort in Algarrobo, Chile, about 100 km (62 mi) west of the capital Santiago. The resort is recognised as having the world's largest swimming pool.

The pool is 1,013 m (3,323 ft) long, covering 8 ha (20 acres), containing some 250 million litres (66 million US gallons) of seawater, with a maximum depth of 35.1 m (115 ft). The water is pumped from the Pacific Ocean, filtered, and treated