Williamson is a census-designated place (CDP) in Yavapai County, Arizona, United States.

[note 1] The name "Wiliamson" is a misnomer, perhaps propagated by federal bureaucratic error; the area has long been known as "Williamson Valley" after the major road through the area, Williamson Valley Road.

[2] According to the United States Census Bureau, the CDP has a total area of 57.6 square miles (149 km2), all land.

[3] Part or all of the area of Williamson historically was referred to as Williamson Valley by area residents and by the county's Board of Supervisors, County Planning Commission, and staff.

The southern portion was long ago called Mint Valley".