The Ollatrim River (Irish: Abhainn Chalatroma) rises in County Tipperary, Ireland. It joins the Nenagh River east of Nenagh town and together they flow into Lough Derg north of Dromineer. A short section of the river forms the border between County Offaly and County Tipperary. The river flows through the Townland of Ollatrim. 
The Ollatrim river, is popular for angling, it holds a stock of wild salmon and trout. The Ormonde Anglers Association were allocated funds to improve areas of both the Ollatrim and Nenagh rivers. There are 15 km of trout fishing on the Ollatrim.
- Ollatrim River Placenames Database of Ireland.
- "Rehabilitation of salmonid production areas in the Nenagh River | Limerick". Fisheriesireland.ie. Retrieved 2013-05-21.