El Calzoncillo Waterfall, Waterfall in Puyehue, Chile.

El Calzoncillo is a waterfall on the northern shore of Lake Rupanco, in the Santa Elvira sector of Puyehue municipality. The Calzoncillo river crosses the northern cliff and drops onto a small beach, where it forms a stream that flows into the lake. The fall has two parts, a long upper stretch and a short lower stretch, and its height is estimated by local residents at between 280 and 404 metres.

In 1858, Guillermo Doll, based at Vega del Rupanco, wrote a description of the waterfall; this is the earliest known written record of the cascade. The name El Calzoncillo, used since the time of the first settlers, comes from its resemblance to the long drawers they wore.

The waterfall's name comes from a playful local observation about its resemblance to long underwear, with three distinct sections that inspired the unusual name. This humorous reference has become part of how the community speaks about the place.

You can reach the waterfall from two vantage points: from below by boat across the lake or from above through private property access. Both routes offer different perspectives on the cascade and allow you to experience it in different ways.

The Calzoncillo river's flow averages 2.1 m³/s, peaking at 4.2 m³/s in July and dropping to 0.1 m³/s in March. No formal survey has been made, so the height quoted by local residents ranges from 280 to 404 m.