Archaeological excavations have shown the human presence in the area of Castelsardo since pre-Nuragic andNuragic times, as well as during theRoman domination in Sardinia.
After the fall of theWestern Roman Empire, the monastery ofNostra Signora di Tergu was founded nearby, but the current town originates from the castle built here, in 1102 (or 1270), by theDoria family ofGenoa. The castle and the village which gradually formed round it where the seat of the Doria's fiefdom in the island calledCastel Doria orCastelgenovese, until it was conquered by theAragonese in the 15th century (1448), and namedCastillo Aragonés (Castel Aragonese). Except for theMaddalena archipelago, it was the last city in the island to join theKingdom of Sardinia.
One of the:I borghi più belli d'Italia (the most beautiful villages of Italy), Les Plus Beaux Villages de la Terre (the most beautiful villages on earth), Città regie della Sardegna (Royal Cities of Sardinia).