The Battle of Cannae () was a key engagement of the Second Punic War between the Roman Republic and Carthage, fought on 2 August 216 BC near the ancient village of Cannae in Apulia, southeast Italy. The Carthaginians and their allies, led by Hannibal, surrounded and practically annihilated a larger Roman and Italian army under the consuls Lucius Aemilius Paullus and Gaius Terentius Varro. It is regarded as one of the greatest tactical feats in military history and one of the worst defeats in Roman history.

Having recovered from their losses at Trebia (218 BC) and Lake Trasimene (217 BC), the Romans decided to engage Hannibal at Cannae, with approximately 86,000 Roman and allied troops. They massed their heavy infantry in a deeper formation than usual, while Hannibal used the double envelopment tactic and surrounded his enemy, trapping the majority of the Roman army, who were then slaughtered. The loss of life on the Roman side meant it was one of the most lethal single days of fighting in history; Adrian Goldsworthy equates the death toll at Cannae to "the massed slaughter of the British Army on the first day of the Somme offensive in 1916". Only about 15,000 Romans, most of whom were from the garrisons of the camps and had not taken part in the battle, escaped death. Following the defeat, Capua and several other Italian city-states defected from the Roman Republic to Carthage.

As news of this defeat reached Rome, the city was gripped in panic. Authorities resorted to extraordinary measures, which included consulting the Sibylline Books, dispatching a delegation led by Quintus Fabius Pictor to consult the Delphic oracle in Greece, and burying four people alive as a sacrifice to their gods. To raise two new legions, the authorities lowered the draft age and enlisted criminals, debtors and even slaves. Despite the extreme loss of men and equipment, and a second massive defeat later that same year at Silva Litana, the Romans refused to surrender to Hannibal. His offer to ransom survivors was brusquely refused. The Romans fought for 14 more years until they achieved victory at the Battle of Zama.

Although for most of the following decades the battle was seen solely as a major Roman disaster, by modern times Cannae acquired a mythic quality, and is often used as an example of the perfect defeat of an enemy army.

Carthage was the capital city of the ancient Carthaginian civilization, on the eastern side of the Lake of Tunis in what is now Tunisia. Carthage was one of the most important trading hubs of the Ancient Mediterranean and one of the most affluent cities of the classical world.

The city developed from a Canaanite Phoenician colony into the capital of a Punic empire which dominated large parts of the Southwest Mediterranean during the first millennium BC. The legendary Queen Alyssa or Dido is regarded as the founder of the city, though her historicity has been questioned. According to accounts by Timaeus of Tauromenium, she purchased from a local tribe the amount of land that could be covered by an oxhide.

The ancient city was destroyed by the Roman Republic in the Third Punic War in 146 BC and then re-developed as Roman Carthage, which became the major city of the Roman Empire in the province of Africa. The city was sacked and destroyed by Umayyad forces after the Battle of Carthage in 698 to prevent it from being reconquered by the Byzantine Empire. It remained occupied during the Muslim period and was used as a fort by the Muslims until the Hafsid period when it was taken by the Crusaders with its inhabitants massacred during the Eighth Crusade. The Hafsids decided to destroy its defenses so it could not be used as a base by a hostile power again. It also continued to function as an episcopal see.

The regional power had shifted to Kairouan and the Medina of Tunis in the medieval period, until the early 20th century, when it began to develop into a coastal suburb of Tunis, incorporated as Carthage municipality in 1919. The archaeological site was first surveyed in 1830, by Danish consul Christian Tuxen Falbe. Excavations were performed in the second half of the 19th century by Charles Ernest Beulé and by Alfred Louis Delattre. The Carthage National Museum was founded in 1875 by Cardinal Charles Lavigerie. Excavations performed by French archaeologists in the 1920s first attracted an extraordinary amount of attention because of the evidence they produced for child sacrifice. There has been considerable disagreement among scholars concerning whether child sacrifice was practiced by ancient Carthage. The open-air Carthage Paleo-Christian Museum has exhibits excavated under the auspices of UNESCO from 1975 to 1984. The site of the ruins is a UNESCO World Heritage Site.