(Feb. 6, 46 BC), in ancient Roman history, battle during the civil war between the Caesarians (Caesar, Julius) and the Pompeians (Pompey the Great) (49–46 BC). Thapsus was a North African seaport about 5 miles (8 km) east of present-day Teboulba, Tunisia. Quintus Metellus Scipio, Pompey's father-in-law, intending to relieve Caesar's siege of Thapsus, drew up his 14 legions and 15,000 cavalry on the corridor of land that formed the northern approach to the city.

Caesar's officers could not restrain their own forces, who surged forward and overwhelmed the enemy and then, completely out of control, slaughtered about 10,000 of them. Cato, who commanded the forces of the North African city of Utica, committed suicide rather than surrender to Caesar. Within three weeks of his victory Caesar had conquered Roman Africa.