The river that separates the Shire from the Old Forest is the Brandywine. It forms the eastern boundary of the Shire and is crossed by the Brandywine Bridge, the route used by travellers heading toward Buckland and the Old Forest.
The river’s Elvish name is Baranduin, meaning “golden-brown river.” “Brandywine” is the Hobbit form of the name, shaped partly by the Hobbits’ pronunciation and folk etymology. Both names refer to the same river, but Brandywine is the standard English name used in descriptions of the Shire.
The Old Forest lies on the eastern side of the river, beyond Buckland. It is an ancient and hostile woodland whose trees are portrayed as unusually aware and unfriendly toward intruders. Frodo, Sam, Merry, and Pippin enter it after leaving the Shire and soon encounter Old Man Willow.
The Withywindle, often confused with the Brandywine, is a different river. It is a tributary that runs through the heart of the Old Forest and is associated with Old Man Willow.