The Salt River is a river in Gila and Maricopa counties in Arizona, United States, that is the largest tributary of the Gila River. The river is about 200 miles (320 km) long. Its drainage basin covers about 13,700 square miles (35,000 km2). The longest of the Salt River's many tributaries is the 195-mile (314 km) Verde River. The Salt's headwaters tributaries, the Black River and East Fork, increase the river's total length to about 300 miles (480 km). The name Salt River comes from the river's course over large salt deposits shortly after the merging of the White and Black Rivers.

Maricopa County is in the south-central part of the U.S. state of Arizona. As of the 2020 census the population was 4,420,568, or about 62% of the state's total, making it the fourth-most populous county in the United States and the most populous county in Arizona, and making Arizona one of the nation's most centralized states. The county seat is Phoenix, the state capital and fifth-most populous city in the United States.