Valencia High School is a high school in Placentia, California under the Placentia-Yorba Linda Unified School District.

Many of Valencia's buildings, including the auditorium and cafeteria, were built during the Great Depression by the WPA.

As of 2024, the school serves a student body of approximately 2,500 students living in southern Placentia and northeast Anaheim. Beginning in the summer of 2010, Valencia underwent a series of renovations and construction projects, including a new 17-classroom building, modernized school breezeway and administration building, and new bleachers at Bradford Stadium. A modernized "quad" was also among the list of projects, serving as a center of campus life and a common location of school activities. Funding for these improvements was provided by Measure A, which was approved by local voters in 2008.

Valencia is the International Baccalaureate (IB) magnet school in PYLUSD. The school's website claims it is one of the best IB programs in Orange County, CA. The school also hosts an advanced technology program called Val Tech, in which students must complete an internship during the summer between their junior and senior years.

The school's mascot is the Tiger, and its team colors are blue and gold.

Kraemer Middle School is near the campus, with a long, narrow parking lot separating the two.