Bagenalstown, officially named Muine Bheag, is a small town on the River Barrow in County Carlow, Ireland.

The Barrow is a river in Ireland. It is one of The Three Sisters; the other two being the River Suir and the River Nore. The Barrow is the longest of the three rivers and, at 192 km (120 mi), the second-longest river in Ireland, behind the River Shannon. The catchment area of the River Barrow is 3,067 km2 before the River Nore joins it a little over 20 km before its mouth. The river's long term average flow rate, again before it is joined by River Nore, is 37.4 cubic metres per second. At the merger with the River Suir, its catchment area is ca. 5,500 km2 and its discharge over 80 m3/s.