Diamond Ranch High School (or DRHS) is a high school that serves students from Diamond Bar and Phillips Ranch, California, United States, and is operated by the Pomona Unified School District (PUSD) in Pomona, California – part of the Greater Los Angeles MSA.

Diamond Ranch's athletic teams compete in the Hacienda League of the CIF Southern Section.

[2] It is situated on a steep hillside on land previously considered unusable.

Because of its modernist architecture, size and location in California, the school has appeared in movies such as The Cell, Orange County, Serenity, Live Free or Die Hard,[6] and The Thinning.

The name was derived from its geographical location at the junction between the City of Diamond Bar and Phillips Ranch, in Pomona, California.