The Viscounty of Àger (Catalan: Vescomtat d'Àger) was a feudal jurisdiction that branched off the County of Urgell in 1094.

Towards 1030 Arnau Mir, Lord of Tost, conquered Àger from the saracens.

Following a period of long-drawn battles Arnau Mir finally conquered Àger in 1047, driving out the saracens from the region for good.

By 1094, when the Catalan nobles were preparing for the conquest of Balaguer further south, Àger became the centre of the newly created Viscounty of Lower Urgell (Vescomtat del Baix Urgell).

This viscounty was given to Guerau II Viscount of Girona, the grandson of Arnau Mir, Lord of Tost.