| Native Name: | Département de l'Arno |
| Common Name: | Arno |
| Subdivision: | department |
| Nation: | the First French Empire |
| Year Start: | 1808 |
| Event Start: | Annexion from the Kingdom of Etruria |
| Date Start: | 25 May |
| Year End: | 1814 |
| Event End: | Treaty of Paris |
| P1: | Kingdom of Etruria |
| Flag P1: | Flag of the Kingdom of Etruria.svg |
| S1: | Grand Duchy of Tuscany |
| Flag S1: | Flag of the Grand Duchy of Tuscany (1840).svg |
| Image Map Caption: | Administrative map of the Italian portion of the French Empire. |
| Capital: | Florence |
| Political Subdiv: | 4Arrondissements |
| Stat Year1: | 1812 |
| Stat Area1: | 8074.75 |
| Stat Pop1: | 584475 |
Arno (in French aʁno/) was a department of the First French Empire in present-day Italy. It was named after the Arno river. It was formed in 1808, when the Kingdom of Etruria (formerly the Grand Duchy of Tuscany) was annexed directly to France. Its capital was Florence.
The department was disbanded after the defeat of Napoleon in 1814. At the Congress of Vienna, the Grand Duchy of Tuscany was restored to its previous Habsburg-Lorraine prince, Ferdinand III. Its territory is now divided between the Italian provinces of Florence, Prato, Arezzo, Pistoia and Forlì-Cesena.
The department was subdivided into the following arrondissements and cantons (situation in 1812):[1]
Its population in 1812 was 584,475, and its area was 807,475 hectares.[1]