The Fellowship crosses the great river Anduin in The Lord of the Rings films.
The Anduin is the longest river in Middle-earth. After leaving Lothlórien, the Fellowship travels down the river in boats before reaching the Falls of Rauros, where the group’s journey changes dramatically.
The river runs southward through much of the continent and passes near important regions including Mirkwood, Lothlórien, and Gondor. Its scale makes it a major geographic feature rather than a small local stream.
The Anduin is sometimes confused with the Bruinen, the river near Rivendell, or the Baranduin, which borders the Shire. Those rivers appear elsewhere in the story and are not the Fellowship’s main downstream route.