Thapsus (less commonly, Tapsus) was an ancient city in what is modern day Tunisia. Its ruins still exist at Ras Dimas near Bekalta , approx. 200 km SE of Carthage. Originally founded by Phoenicians, it served as a marketplace on the coast of the province Byzacena in Africa Propria. Thapsus was established near a salt lake on a point of land eighty stadia (14.8 km) from the Island of Lampadusa .

In 46 BC, Julius Caesar defeated Metellus Pius Scipio and the Numidian King Juba with a tremendous loss of men near Thapsus (see Battle of Thapsus). Caesar exacted a payment of 50,000 sesterces from the vanquished. Their defeat marked the end of opposition to Caesar in Africa. Thapsus then became a Roman colony.

The city should not be confused with the medicinal herb Verbascum thapsus.