Brunswick River is a river in the South West region of Western Australia.

The river rises in the Darling Range then flows south-west discharging into the Collie River near Australind.

The river was named in 1830 by Lieutenant-Governor James Stirling after Ernest Augustus, King of Hanover, Duke of Brunswick and Lüneburg, the fifth son and eighth child of George III.

Over a period of five days in December 1813, while in command of HMS Brazen, Captain Stirling took the duke and his entourage to Wijk aan Zee in Holland.

[3] The Brunswick has six tributaries: Wellesley River, Ernest River, Elvira Gully, Augustus River, Frederic River and Lunenburgh River.