The Wimmera River is a river in Western Victoria, Australia. It begins in the Pyrenees, and flows northwards into Lake Hindmarsh and Lake Albacutya and, exceptionally, into a chain of ephemeral lakes further north in Wyperfeld National Park and the Big Desert Wilderness Park. In most years flows do not reach these terminal lakes and the river contracts to a series of pools. Its major tributaries include Mount William Creek and the MacKenzie River. The northernmost terminal section is known as Outlet Creek. The Wimmera River is one of a handful of northward flowing rivers and their associated distributaries in Victoria that do not join the Murray River.
Water use and quality 
Major towns the Wimmera River flows through are Horsham, Dimboola and Jeparit. The inflowing of saline groundwater into the lower reaches of the Wimmera River in recent years has severely affected the water quality, making the water more saline than sea water in several locations.
The health of the Wimmera River is expected to improve under the Wimmera-Mallee pipeline project, completed in 2008. The Project involved replacing old, inefficient stock water supply and irrigation infrastructure, with a pipeline system. Prior to the project's completion, up to 90 percent of water extracted from the Wimmera river was lost through evaporation and seepage. The Wimmera-Mallee Pipeline system will be many times more efficient and means there will be much less water extracted from the Wimmera river. This should reduce the quantities of water taken from the river and could thereby result in an increase in environmental flows in the river system. (see discussion)
Horsham flooding 
Western Highway crossing the Wimmera River at Horsham
- 4.71m - January 2011.
- 3.87m - October 1894 Major flood along the Wimmera River, including Dunmunkle Creek and Yarriambiack Creek. Townships of Horsham, Glenorchy, Rupanyup, Warracknabeal, Dimboola and Jeparit affected.
- 3.87m - August 1909. Major flood along the Wimmera River, including Dunmunkle and Yarriambiack Creeks. Townships of Horsham, Glenorchy, Rupanyup, Warracknabeal, Dimboola and Jeparit affected.
- 3.73m - September 1916, major flood along the Wimmera River affected the townships of Glenorchy and Horsham.
- 3.55m - August 1981, flood affected the Wimmera River and Yarriambiack Creek.
- 3.49m - October 1996.
- 3.32m - September 2010 
- 3.30m - October 1992.
Coordinates: 37°16′29″S 143°15′00″E / 37.27472°S 143.25000°E