The province of Alessandria (Italian: provincia di Alessandria; Piedmontese: provincia ëd Lissandria; in Piedmontese of Alessandria: provinsa ëd Lissändria) is an province of the region of Piedmont in Italy. The capital is the city of Alessandria. It has a population of 407,029 across its 187 municipalities as of 2025.
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. To the north it borders on the province of Vercelli and to the west on the Metropolitan City of Turin and the province of Asti. It shares its southern border with Liguria (province of Savona and the Metropolitan City of Genoa). Its south-east corner touches the Province of Piacenza in Emilia Romagna, while to the east it borders on the Lombard province of Pavia.