Río Pillanleufú is a freestone river flowing through the Futrono area of the Los Ríos Region in southern Chile. Draining the southern and eastern slopes of the Mocho-Choshuenco volcano, the river runs in a north-south direction along the Liquiñe-Ofqui Fault before emptying into Lago Maihue, which in turn drains via the Río Calcurrupe into Lago Ranco. The river's name comes from Mapudungun, meaning "river of the pillán" — a reference to the volcanic spirits of Mapuche tradition, fitting for a river born from the flanks of an active volcanic complex. The watershed is part of the larger Bueno River Basin, and the river's character reflects the rugged, heavily forested landscape of the Chilean Lake District, with canyon sections, gradient changes, and the kind of cold, clear water that defines some of Patagonia's most productive trout and salmon fisheries.