The modern name Athlone comes from the Irish Ath-Luain the ford of Luain. According to tradition a man called Luan, the son of Lewy kept a hostelry close to the ford. He acted as a guide to travellers who needed to venture across the rapid torrent. In time the place came to be known as Athlone or Ath Luain: the ford of Luain.

The military history of the town dates back to antiquity. The ford of Athlone is strategically important, as south of Athlone the Shannon is impassable until Clonmacnoise. The current battlements and cannon emplacements were installed to prevent a French fleet from sailing up the Shannon and establishing a bridgehead in Lough Ree (likewise south of Athlone at Shannonbridge, near Clonmacnoise). The idea, mooted during the Elizabethan wars, of relocating the Lord Deputy of Ireland here from Dublin further illustrates the strategic importance of the town. Other fortifications include the ruins of a battery just to the north of Athlone and a large artificial hill called "The Batteries" upon which council housing has been built. On the Leinster side of the town, remains of defences built in the 19th century to help thwart a French attack still exist, particularly around the offices of the Town council. The Connaught side was defended by a fosse which no longer exists.