Cadiz represents the Sem. Agadir, Gadir, or Gaddir ("stronghold") of the Carthaginians, the Gr. Gadeira, and the Lat. Gades. Tradition ascribes its foundation to Phoenician merchants from Tyre, as early as 1100 B.C.; and in the 7th century it had already become the great mart of the west for amber and tin from the Cassiterides (q.v.). About 501 B.C. it was occupied by the Carthaginians, who made it their base for the conquest of southern Iberia, and in the 3rd century for the equipment of the armaments with which Hannibal undertook to destroy the power of Rome. But the loyalty of Gades, already weakened by trade rivalry with Carthage, gave way after the second Punic War. Its citizens welcomed the victorious Romans, and assisted them in turn to fit out an expedition against Carthage. Thenceforward, its rapidly-growing trade in dried fish and meat, and in all the produce of the fertile Baetis (Guadalquivir) valley, attracted many Greek settlers; while men of learning, such as Pytheas in the 4th century B.C., Polybius and Artemidorus of Ephesus in the 2nd, and Posidonius in the 1st, came to study the ebb and flow of its tides, unparalleled in the Mediterranean. C. Julius Caesar conferred the civitas of Rome on all its citizens in 49 B.C.; and, not long after L. Cornelius Balbus Minor built what was called the "New City," constructed the harbour which is now known as Puerto Real, and spanned the strait of Santi Petri with the bridge which unites the Isla de Leon with the mainland, and is now known as the Puente de Zuazo, after Juan Sanchez de Zuazo, who restored it in the 15th century.

Under Augustus, when it was the residence of no fewer than 500 equites, a total only surpassed in Rome and Padua, Gades was made a municipium with the name of Augusta Urbs Gaditana, and its citizens ranked next to those of Rome. In the 1st century A.D. it was the birthplace or home of several famous authors, including Lucius Columella, poet and writer on husbandry; but it was more renowned for gaiety and luxury than for learning. Juvenal and Martial write of Jocosae Gades, "Cadiz the Joyous," as naturally as the modern Andalusian speaks of Cadiz la Joyosa; and throughout the Roman world its cookery and its dancing-girls were famous. In the 5th century, however, the overthrow of Roman dominion in Spain by the Visigoths involved Cadiz in destruction. A few fragments of masonry, submerged under the sea, are almost all that remains of the original city. Moorish rule over the port, which was renamed Jezirat-Kadis, lasted from 711 until 1262, when Cadiz was captured, rebuilt and repeopled by Alphonso X. of Castile. Its renewed prosperity dates from the discovery of America in 1492. As the headquarters of the Spanish treasure fleets, it soon recovered its position as the wealthiest port of western Europe, and consequently it was a favourite point of attack for the enemies of Spain. During the 16th century it repelled a series of raids by the Barbary corsairs; in 1587 all the shipping in its harbour was burned by the English squadron under Sir Francis Drake; in 1596 the fleet of the earl of Essex and Lord Charles Howard sacked the city, and destroyed forty merchant vessels and thirteen warships.

This disaster necessitated the rebuilding of Cadiz on a new plan. Its recovered wealth tempted the duke of Buckingham to promote the fruitless expedition to Cadiz of 1626; thirty years later Admiral Blake blockaded the harbour in an endeavour to intercept the treasure fleet; and in 1702 another attack was made by the British under Sir George Rooke and the duke of Ormonde. During the 18th century the wealth of Cadiz became greater than ever; from 1720 to 1765, when it enjoyed a monopoly of the trade with Spanish America, the city annually imported gold and silver to the value of about £5,000,000. With the closing years of the century, however, it entered upon a period of misfortune. From February 1797 to April 1798 it was blockaded by the British fleet, after the battle of Cape St Vincent; and in 1800 it was bombarded by Nelson. In 1808 the citizens captured a French squadron which was imprisoned by the British fleet in the inner bay. From February 1810 until the duke of Wellington raised the siege in August 1812, Cadiz resisted the French forces sent to capture it; and during these two years it served as the capital of all Spain which could escape annexation by Napoleon. Here, too, the Cortes met and promulgated the famous Liberal constitution of March 1812. To secure a renewal of this constitution, the citizens revolted in 1820; the revolution spread throughout Spain; the king, Ferdinand VII., was imprisoned at Cadiz, which again became the seat of the Cortes; and foreign intervention alone checked the movement towards reform.

A French army, under the duc d'Angoulême, seized Cadiz in 1823, secured the release of Ferdinand and suppressed Liberalism. In 1868 the city was the centre of the revolution which effected the dethronement of Queen Isabella.

See Sevilla y Cadiz, sus monumentos y artes, su naturaleza é historia, an illustrated volume in the series "España," by P. de Madrazo (Barcelona, 1884); Recuerdos Gaditanos, a very full history of local affairs, by J.M. León y Dominguez (Cadiz, 1897); Historia de Cadiz y de su provincia desde los remotos tiempos hasta 1824, by A. de Castro (Cadiz, 1858); and Descripcion historico-artistica de la catedral de Cadiz, by J. de Urrutia (Cadiz, 1843).