The Río Llollelhue is a 95-kilometer river flowing through the Los Ríos Region of southern Chile, draining waters between Lago Ranco and the Río Valdivia basin before emptying into the Río Bueno. The river originates near Futrono at the northern end of Lago Ranco, passes through the commune of Paillaco, and flows past the city of La Unión before joining the Río Bueno just over 2 kilometers east of where the Río Pilmaiquén meets the Bueno. With an average flow of approximately 15 m³/s, the Llollelhue is the most significant northern tributary of the Río Bueno. Its principal tributary is the Río Radimadi, and it also receives contributions from smaller rivers including the Palitrán, Traiguén, Treguatraiguén, Lilcopulli, Los Patos, Las Ánimas, and Cartmehuida, which enter primarily from the north. The river passes through a landscape dominated by temperate oceanic climate, fertile agricultural valleys, and remnant native forests, making it a scenic and productive destination for anglers exploring southern Chile.