|Département de la Sésia|
|Department of the First French Republic and of the First French Empire|
|-||Decree of 24 Fructidor, year X||11 September 1802|
|-||Treaty of Fontainebleau||11 April 1814|
|-||1812||3,351.18 km2 (1,294 sq mi)|
|Density||60.5 /km2 (156.7 /sq mi)|
|Political subdivisions||5 Arrondissements|
Sésia was a department of the French Consulate and of the First French Empire in present-day Italy. It was named after the Sesia river. It was formed in 1802, when the Subalpine Republic (formerly the mainland portion of the Kingdom of Sardinia) was directly annexed to France. Its capital was Vercelli.
The department was disbanded after the defeat of Napoleon in 1814. At the Congress of Vienna, the Savoyard King of Sardinia was restored in all his previous realms and domains, including Piedmont. Its territory is now divided between the Italian provinces of Vercelli and Biella.
- Vercelli, cantons: Agnona, Crevacuore, Gattinara, Masserano, Quinto, Stroppiana, Trino and Vercelli (2 cantons).
- Biella, cantons: Biella, Bioglio, Cacciorna, Candelo, Cavaglià, Cossato, Graglia, Mongrando and Mosso Santa Maria.
- Santhià, cantons: Buronzo, Cigliano, Crescentino, Livorno and Santhià.
Its population in 1812 was 202,733, and its area was 335,118 hectares.