Cagliari is the capital of the island of Sardinia, an autonomous region of Italy.

Cagliari is called Casteddu (literally, the castle) in the Sardinian language. It has about 165,000 inhabitants, or about 300,000 including the suburbs (metropolitan area) (Elmas, Pirri, Selargius, Monserrato, Quartucciu, Quartu Sant'Elena).

Under the name of Karalis it was one of a string of Phoenician trading colonies in Sardinia, including Sulcis, Nora, and Tharros, that were founded from Tyre in the 7th century. It passed with the rest of the island first to the control of Carthage and then to Rome in 238 BC when the Romans defeated the Carthaginians.

Subsequently ruled in turn by the Vandals and the Byzantine Empire, became the eponymous capital of an independent kingdom or "giudicato", ruled by a "giudice" or "judike" (literally judge). However, there is some evidence that during this period of independence from external rule, Cagliari was deserted because too exposed to attacks by Moorish pirates from the sea. Apparently many people left Cagliari and founded a new town in an area close to the Santa Gilla swamp on the west of Cagliari, but distant from the sea. The "giudicato" of Karalis comprised a large area of the Campidano plain, the mineral resources of the Sulcis region and the mountain region of Ogliastra. Apart from Karalis, there were other three independent and autonomous kingdoms, or "giudicati", in Sardinia: Torres in the north west, Gallura in the north east, and the most famous and long-lived Arborea, with Oristano (Aristanis in Sardinian language) as capital.

In the 11th century, the Pisan republic that had previously seized the Sulcis region in the south east, conquered the kingdom of Karalis and re-built the town of Cagliari. Pisa was one of the four Italian "maritime republics" that in the middle age fought for control of the Mediterranean sea and its commercial routes. The other maritime republics were the short-lived Amalfi, Genoa and Venice. Pisa and Genoa had a keen interest in Sardinia because it was a perfect strategic base for controlling the commercial routes between Italy and North Africa.

Some of the fortifications that still surround the current district of Castello (Casteddu 'e susu in Sardinian language) were built by the Pisans, most notably the two remaining white lime-stone towers designed by architect Giovanni Capula (originally there were three towers that guarded the three gates that gave access to the district). Together with the district of Castello, Cagliari comprised the districts of Marina (which included the port), Stampace and Villanova. Marina and Stampace were guarded by walls, while Villanova, which mainly hosted peasants, was not.

In the 14th century the kingdom of Aragon conquered Cagliari after a battle against the Pisans and advanced its plan to conquer all of Sardinia. When Sardinia was finally conquered by Aragon, Cagliari (during the Catalan domination the city was named Càller), became the administrative capital of the vice-kingdom of Sardinia, which later came under the rule of the Spanish empire. Many agree that the Spanish domination was a period of decadence for Cagliari and Sardinia.

In the 18th century, after a brief rule of the Austrian Habsburgs, Cagliari and Sardinia came under the House of Savoy in 1720. As ruler of Sardinia, the Savoys took the title of kings of the Sardinian kingdom. The Sardinian kingdom comprised Savoy and Nice (currently in France), Piedmont and Liguria, as well as Sardinia. Although Sardinian by name, the kingdom had its capital in Turin, in mainland Italy, where the Savoys resided. The parliament was also in Turin and its memebers were mainly aristocrats from Piedmont or the mainland. By the end of the 18th century, after the French Revolution, France tried to conquer Cagliari because of its strategic role in the Mediterranean sea. A French army landed in the Poetto beach and moved towards Cagliari, but the French were defeated by Sardinians who decided to defend themselves against the revolutionary army. People from Cagliari hoped to receive some concession from the Savoys in return for their defending the town: for example, aristocrats from Cagliari asked for a Sardinian representative in the parliament of the kingdom. When the Savoys refused any concession to the Sardinians, inhabitants of Cagliari rose up against the Savoys and expelled all representatives of the kingdom and people from Piedmont. This insurgence is celebrated in Cagliari during the "Die de sa Sardigna" (Sardinian Day) on the last weekend of April. However the Savoys regained control of the town after a brief period of autonomous rule.

From the 1870s, with the unification of Italy, the city experienced a century of rapid growth. Many outstanding buildings were erected by the end of the 18th century during the office of Mayor Ottone Bacaredda. Many of these buildings combined influences from Art Nouveau together with the traditional Sardinian taste for flower decoration: an example is the white marble City Hall near the port. Ottone Bacaredda is also famous for the violent repression of one of the earlier worker strikes in the beginning of the 20th century.

During the Second World War, Cagliari was heavily bombed by the Allies in February 1943. In order to escape from the bombardments and the misery of the destroyed town, many people left Cagliari and moved to the country or rural villages, often living with friends and relatives in overcrowded houses. This flee from the town is knwon as "sfollamento" (deserting). After the Italian truce with the Allies in September 1943, the German Army took control of Cagliari and the island, but soon retreated peacefully in order to reinforce their positions in mainland Italy. The American Army then took control of Cagliari. Cagliari was strategically important during the war because of its location in the Mediterranean Sea. Many airports were near Cagliari (Elmas, Monserrato, Decimomannu, currently a NATO airbase) from which airplanes could fly to Northern Africa or mainland Italy and Sicily.

After the war, the population of Cagliari boosted and many apartment blocks were erected in new residential districts, often created with poor planning as for recreational areas.

Cagliari is home to the football team Cagliari Calcio, winner of the Italian league championship in 1970, with the team led by one of the greatest Italian strikers of all times, Gigi Riva.

The old part of the city (called 'Castello', the castle) lies on top of a hill, with a wonderful view of the Gulf of Cagliari (aka Angels Gulf). Most of its city walls are intact, and feature the two 13th century white lime-stone towers, St. Pancras tower and the Elephant tower. The local white lime-stone was also used to build the walls of the city and many builidings. D.H. Lawrence, in his memories of a trip in Sardinia, "Sea and Sardinia", described the impressive effect of the warm Mediterranean sun-light on the white lime-stone city and compared Cagliari to a "white Jerusalem".

In Castello you can visit the Cathedral, which was repaired in the 1930s turning the former Baroque facade into a Medieval Pisan style facade, more akin to the original appearance of the church. Near the Cathedral is the palace of the Provincial Government (which used to be the island's governor's palace before 1900). In Castello is also the Sardinian Archaeological Museum, the biggest and most important regarding the prehistoric Nuragic civilisation of Sardinia. Finally, Castello hosts many craftsmen workshops in its tightened and scenic lanes.

The other early districts of the town(Marina, Stampace, Villanova) retain much of their original appeal and still seem to function as distinct villages within the town.

Cagliari was inhabited since pre-historic periods for its favourable position between the sea and a fertile plain, its being sourrounded by two swamps (which afforded defences from enemies from inner lands) and its vicinity to high and green mountains (to which people could evacuate if everything else was lost). Some testimonies of pre-historic inhabitants were found in Monte Claro and in Cape Sant'Elia. An outstanding testimony of the Roman domination is the Roman Amphitheatre . This is a unique monument in the world because it is the only Roman amphitheatre carved into a block of rock (the typical lime-stone on which Cagliari is built). The Amphitheatre still stages open-air operas and concerts during the summer.

The districts built in the 1930s spot some nice examples of Art Deco artichecture and some controversial examples of Fascist neoclassicism, such as the Justice Court (Palazzo di Giustizia) in the Republic Square. The Justice Court is close to the biggest town park, Monte Urpinu, with its pine trees and artificial lakes. The park includes a vast area of a hill. Visitors can reach the top of the hill by car and enjoy a nice view of Castello district, the gulf, the swamps and the beach.

Cagliari has one of the longest beaches in an Italian town. The Poetto beach stretches for 13 km. and was famous for its white fine-grained sand. A recent controversial intervention to save the beach from erosion has slightly altered the original texture of the sand.

Cagliari is an ideal location for sailing,hiking and outdoor sports. It has a mild climate, often refreshed by northern-west winds. It is close to other beautiful sea-side locations, such as Chia or Villasimius, still relatively unspoilt by tourism and is also close to mountain parks, such as Monte Arcosu or Maidopis, with large forests and wildlife (Sardinian deers, wild boars, etc.).

Cagliari has some peculiar gastronomic traditions. Many dishes are based on the wide variety of fish and sea food available. Although it is possible to trace influences from Spanish gastronomy, Cagliaritanian food has a distintctive and unique character. Very good wines are also part of Cagliaritanians' dinners: excellent wines are in fact produced in the nearby vineyards of the Campidano plain.

Life in Cagliari has been vividly depicted by Sergio Atzeni , who settled many of his novels and short stories in ancient and modern Cagliari. Among these, available in English is "Bakunin's son".

A church in Cagliari gives its name to Buenos Aires. The Spaniard that founded Buenos Aires visited the church of Bonaria (fair winds)and asked for help from the Mary of Bonaria, to whom the church is dedicated. The church faces the sea and was allegedly built where a sailor landed after the Mary of Bonaria appeared in the midst of a tempest and saved the sailor and his ship from sinking.