Coordinates: 36°54′N 7°46′E / 36.9°N 7.767°E / 36.9; 7.767

Hippo Regius (Hippone) is the ancient name of the modern city of Annaba, in Algeria. Under this name, it was a major city in Roman Africa, hosting several early Christian councils, and was the home of the philosopher and theologian Augustine of Hippo. In even earlier days, the city was a royal residence for Numidian kings.

Hippo was a Tyrian colony on the west coast of the bay to which it gave its name: Hipponensis Sinus, first settled by the Phoenicians probably in the 12th century BC; the surname Regius 'of the King' was bestowed on it as one of the places where the Numidian kings resided.

A maritime city near the mouth of the river Ubus, it became a Roman colonia which prospered and became a major city in Roman Africa. It is perhaps most famous as the bishopric of Saint Augustine of Hippo in his later years. In the summer of 430 the Vandals put the city of Hippo under siege as the aged bishop lay on his death bed; he died 28 August 430. Following a 14-month siege, the city fell to the Vandals and King Geiseric made it the capital of the Vandal kingdom until the capture of Carthage in 439.

Augustine of Hippo ( /ɒˈɡʌstɨn/ or /ˈɔːɡəstɪn/;Latin: Aurelius Augustinus Hipponensis; November 13, 354 – August 28, 430), also known as Augustine, St. Augustine, St. Austin,St. Augoustinos, Blessed Augustine, or St. Augustine the Blessed, was Bishop of Hippo Regius (present-day Annaba, Algeria). He was a Latin philosopher and theologian from Roman Africa. His writings were very influential in the development of Western Christianity.

According to his contemporary, Jerome, Augustine "established anew the ancient Faith." In his early years he was heavily influenced by Manichaeism and afterward by the Neo-Platonism of Plotinus. After his conversion to Christianity and baptism in AD 387, Augustine developed his own approach to philosophy and theology, accommodating a variety of methods and different perspectives. He believed that the grace of Christ was indispensable to human freedom, and he framed the concepts of original sin and just war.

When the Western Roman Empire was starting to disintegrate, Augustine developed the concept of the Catholic Church as a spiritual City of God (in a book of the same name), distinct from the material Earthly City. His thoughts profoundly influenced the medieval worldview. Augustine's City of God was closely identified with the Church, the community that worshipped God.