Lough Allen (Loch Aillionn in Irish) is a lake situated on the River Shannon between the West and Northwest of the Republic of Ireland, near Ireland's border region. The lake lies to the south of the river's source, near the Iron Mountains, and is the uppermost of the three main lakes on the river. The other two, Lough Ree and Lough Derg are both much further to the south.
- See also: List of Irish lochs and loughs
