Kelvin is an unincorporated community in Pinal County, Arizona, United States.

Kelvin is located near the Gila River, 24.6 miles (39.6 km) east-northeast of Florence.

The post office and original old west town site retained the name of Kelvin.

This group of small communities are all located within a two-mile circumference from each other and many of the old foundations of Kelvin's original town site still exist.

The ruins of the adobe post office are still partly standing near the junction of the Florence / Kelvin Highway and Ray Road.