State Route 266 (SR 266) is a highway in Graham County, Arizona that runs from its junction with US 191 south of Safford to Fort Grant.

[2] SR 266 travels through sparsely populated areas and does not pass through any cities or towns.

It serves primarily as an access road to Fort Grant.

[1][3] SR 266 was designated in 1957 as a state route from US 666 (now US 191) to Fort Grant.

Route is the access road to Fort Grant State Prison just north of Bonita, Arizona.