Diyala is one of the constituent provinces of the nation of Iraq. It extends to the northeast of Baghdad as far as the Iranian border. Its capital is Baquba.
Diyala province covers an area of 17,685 km². In 2003, it had an estimated population of some 1,271,000 people, mostly Sunni Arabs and Kurds. A large portion of the province is drained by the Diyala River, a major tributary of the Tigris.
The province is further divided into six districts: