|Native name||An Bhrosnach|
|Etymology||Possibly means "place of twigs"|
|Main source||Near Mullingar, County Westmeath|
|River mouth||Atlantic via the River Shannon|
|Length||79.26 kilometres (49.25 mi)|
|Basin size||1,248 km2 (482 sq mi)|
The River Brosna is 49.25 miles (79 km) in length.
The Brosna begins as a small river, flowing from Lough Owel in a south-south-westerly direction through Mullingar, into Lough Ennell. From Lough Ennell, the river Brosna flows into Kilbeggan, where it still powers the mill at Kilbeggan Distillery. The Brosna continues flowing southwest through Clara, Ballycumber and Pullough. East of Ferbane it is joined by the Silver River. From Ferbane it heads to Shannon Harbour, north of Banagher, where it joins the Shannon.
The river Brosna is popular for fly fishing and has stocks of brown trout as well as some salmon and grilse. However it has, in recent years, suffered somewhat from pollution problems due to its poor assimilative capacity and the discharge of untreated sewage in the Mullingar area during storm conditions. There have also been discharges of pollutants, whether accidental or otherwise, such as one filmed at the bridge of Clonmore industrial estate in Mullingar.  
Works, to the cost of IR £750,000, were undertaken on the river in the late 1940s and early 1950s to improve drainage in the river’s catchment area. As part of the Arterial Drainage Scheme, designed to tackle poor drainage caused by Ireland’s relatively low-lying topography, the river was deepened and widened, leaving the river with the high banks distinctive of many of the rivers in the Irish midlands that received this treatment. More recently, in late 2008 the river was diverted from the N52 road beside Mullingar in order to accommodate a new roundabout and bridge.
- "Archived copy". Archived from the original on 2007-09-27. Retrieved 2007-03-21..
- Ordnance Survey of Ireland: Rivers and their Catchment Basins 1958 (Table of Reference)
- Film of discharge into the River Brosna
- ”Over 50% of Brosna Polluted”, Westmeath Examiner, July 21st, 2001.
- "Archived copy". Archived from the original on 2011-06-07. Retrieved 2007-03-21..
- An investigation of the effects of an arterial drainage scheme on the rainfall-runoff transformation behaviour of the Brosna catchment in Ireland, Bhattarai, K. P., O'Connor, K. M., EGS - AGU - EUG Joint Assembly, Abstracts from the meeting held in Nice, France, 6–11 April 2003, abstract #12112.
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