Historical region, southeastern France and northwestern Italy. From the 11th century the counts of Savoy ruled it as part of the kingdom of Arles under the suzerainty of what would become the Holy Roman Empire. It became virtually independent and expanded across the Alps to include the plain of Piedmont in Italy. In the 18th century Piedmont and Savoy were incorporated into the kingdom of Sardinia, and the dukes of Savoy became kings of Sardinia. Savoy and Piedmont were ceded to France in 1792, but Savoy was restored to its traditional rulers in 1815, with the addition of Genoa. In 1860 Sardinia, Genoa, and Piedmont joined other Italian states to form the Kingdom of Italy. The house of Savoy was the ruling house of Italy until 1946, when the Italian Republic was established.