The River Slaney is a large river in the southeast of Ireland. It rises on Lugnaquilla Mountain in the western Wicklow Mountains and flows west and then south through counties Wicklow, Carlow and Wexford for 117.5 km (73 mi), before entering St George's Channel in the Irish Sea at Wexford town. The estuary of the Slaney is wide and shallow and is known as Wexford Harbour. The catchment area of the River Slaney is 1,762 km2. The long term average flow rate of the River Slaney is 37.4m3/s

The Wicklow Mountains form the largest continuous upland area in Ireland. They occupy the whole centre of County Wicklow and stretch outside its borders into the counties of Dublin, Wexford and Carlow. Where the mountains extend into County Dublin, they are known locally as the Dublin Mountains. The highest peak is Lugnaquilla at 925 metres.