The province of Cagliari (Italian: provincia di Cagliari; Sardinian: provìntzia de Casteddu) was a province in the autonomous island region of Sardinia, Italy.

It had an area of 4,470 square kilometres (1,730 sq mi), and a total population of 543,310 (2001).

The historical province was suppressed by the 2016 Regional Decree Province of Cagliari and replaced by the Metropolitan City of Cagliari and by the province of South Sardinia.

The valley of Piscinamanna is in the province.

As of June 30, 2005, the major comuni (municipalities) by population was: The Democratic Party (Italian: Partito Democratico, PD) is a social-democratic political party in Italy, with The People of Freedom (Italian: Il Popolo della Libertà, PdL), it is one of the two major parties of the current Italian party system.