Crotalus ruber, also known as the Red Diamond Rattlesnake, is a venomous pit viper species found in southwestern California in the United States and Baja California in Mexico.

Crotalus ruber is very similar in pattern to C. atrox, but it is distinguished by its reddish color, to which the specific name, ruber, refers. Also, the first lower labial scale on each side is transversely divided to form a pair of anterior chin shields.

The United States in southwestern California, and Mexico in Baja California, except for the cape region of lower Baja California.