The province of Alessandria (Italian: provincia di Alessandria; Piedmontese: provincia ëd Lissandria; in Piedmontese of Alessandria: provinsa ëd Lissändria) is an Italian province, with a population of some 425,000, which forms the southeastern part of the region of Piedmont.

With an area of 3,558.83 square kilometres (1,374.07 sq mi) it is the third largest province of Piedmont after the province of Cuneo and the Metropolitan City of Turin.

It shares its southern border with Liguria (province of Savona and the Metropolitan City of Genoa).

It is one of the nine Sacri Monti of Piedmont and Lombardy, included in UNESCO World Heritage list.

Its construction began in 1589, around a former Sanctuary of St. Mary whose creation is traditionally attributed to Saint Eusebius of Vercelli around 350 AD.