The Val di Chiana, Valdichiana, or Chiana Valley is an alluvial valley of central Italy, lying on the territories of the provinces of Arezzo and Siena in Tuscany and the provinces of Perugia and Terni in Umbria.
The Val di Chiana is about 100 km long, and covers about 2300 km². It runs north to south between the plain of Arezzo and the plain of Orvieto and includes the watershed of the Canale Maestro della Chiana, its main watercourse, and the northern part of the watershed of the Chiani River.
To the north-east it is bounded by the Tuscan pre-Apennines crowned by the Alta Sant'Egidio (1,057 m), monte Lignano (837 m) and monte Corneta (744 m). To the south-east, it reaches Lake Trasimeno and the valley of the Nestore River. To the west, it extends to the Val d'Orcia, where it reaches its highest altitude, 1,148 m (Monte Cetona).
The landscape is mostly hilly, with a plain around the Canale Mastro. Its mean altitude is around 405 m.
- Chianina, a breed of cattle which originated in the valley.
- Val di Chiana map by Leonardo da Vinci.