The Santa Maria River is an intermittent stream located in western Arizona.

It is a primary tributary of the Bill Williams River and one of the main sources of inflow for Alamo Lake.

The river forms a portion of the boundary between Mohave and La Paz counties.

The Santa Maria River is formed by the confluence of the Sycamore and Kirkland Creeks, about 10 miles (16 km) east of the community of Bagdad.

During periods of heavy rainfall, the lake may extend beyond the confluence point, during which period the Santa Maria empties directly into the lake rather than joining the Big Sandy River.