Laguna Avendaño is a lake located in the comuna of Quillón, provincia de Diguillín, within the Ñuble Region of Chile. It sits at an elevation of 270 meters above sea level and covers approximately 15 square kilometers (around 160 hectares). The lake has an average depth of 8 meters, and its shorelines are notably gentle, without pronounced slopes. When viewed from above — particularly from the nearby cerro Cayumanqui, an emblematic hill of the Quillón area — the lake's surface takes on the outline of a whale, a distinctive geographical curiosity. The lake lies within the drainage basin of the río Itata.

The surrounding landscape consists of native forests and hills that frame the water on multiple sides. The lake supports a variety of wildlife, including black-necked swans, herons, and wild ducks, making it a reasonable spot for wildlife observation while on the water. Swans and ducks are regularly present and accustomed to human activity in the area.

Laguna Avendaño is an established venue for water sports, with kayaking, sailing, water skiing, and canoeing all practiced here. The lake has hosted organized sailing competitions, including the Campeonato Asovela Quillón, which drew more than 30 vessels in a recent edition, indicating that the water is suitable for multi-vessel activity. The shores are calm enough for recreational paddling and are described as appropriate for children as well as adults.

The Parque Laguna Avendaño, managed by the Municipalidad de Quillón, provides developed facilities along the waterfront, including lighting, food vendors, artisan stalls, and designated recreational and family areas. Camping and picnic areas are also available in the vicinity. The park functions as the primary tourist draw for both Quillón and the broader Ñuble Region, with peak activity concentrated during the summer months, when it serves as a significant source of local employment. Visitor numbers are highest in summer, which corresponds to the Southern Hemisphere warm season (December through March).