Estado de Occidente (also known as Sonora y Sinaloa) was a Mexican state established in 1824. The constitution was drafted in that year and the government was initially established with its capital at El Fuerte, Sinaloa. The first governor was Juan Miguel Riesgo. The state consisted of modern Sonora and Sinaloa, and also modern Arizona more or less south of the Gila River (although in much of this area the Yaqui, Pima, Apaches, and other native inhabitants did not recognize the authority of the state),

The constitution was established in 1825 with one of its principals being the making of all inhabitants of the state citizens. This was resented by the Yaqui since they now had to pay taxes, which they had been exempt from before. The Yaqui also considered themselves possessed of sovereignty and territorial rights which were threatened by the states new constitution.

This led to a new outbreak of war between the Mexicans and the Yaquis (see Yaqui Wars) with Juan Banderas as the leader of the Yaqui forces. As a result of this war the capital of Occidente was moved to Cosala.

Sonora and Sinaloa were again split into two separate states in 1830.