Alghero is situated in north-west Sardinia, on the bay of the same name. Most of the region north of the urban area is taken up by the Nurra plain.
In the farthest north-west fringe the Carsic cliffs of Capo Caccia, Punta Giglio and Monte Doglia rise up. Towards the south the town borders on the plateaus of Villanova Monteleone and Bosa.
Alghero constitutes a linguistic island in the island of Sardinia, for approximately a quarter of its inhabitants still speak Catalan today.
Its coastline is known also as the Riviera del Corallo; the red coral fished in its waters is among the most precious in the world. The name Alghero is usually said to derive from "Aleguerium" (alga), due to the large quantity of seaweed (to be precise, Posidonia Oceanica) that gets deposited on its shores.