A town of Grey county, South Australia, 305 m. by rail S.E. of Adelaide. It stands on the northern base of the mountain of the same name, an extinct volcano. It is a handsome town with many fine buildings of white limestone and grey and red dolomite, which abound in the neighbourhood, the church of St Paul being the finest edifice of its kind outside Adelaide. The agricultural society has a good showground where two shows are held annually. Two splendid lakes lie near the town - Blue Lake, 160 acres in extent, and Valley Lake, 97 acres, from the first of which the water-supply of the town is derived. Mount Gambier is the centre of one of the richest grain-growing districts in Australia. Pop. (1901), 3162; and including the suburbs, about 8000.