Hayward High School is a public high school in Hayward, California, United States, serving students living in northern Hayward and portions of Castro Valley, Cherryland and Fairview. It is one of four high schools in the city and is one of the oldest high schools in Northern California. The school's official mascot is the "Farmer", which dates back to Hayward's period as an agricultural center. Its emblem features a farmer with a plow, a reference to the city's agricultural past.

Founded in 1892, Hayward High is one of the oldest high schools in the San Francisco Bay Area. The first true high school that opened in 1893 was called Union High School #3. It served students from Hayward, Castro Valley, San Lorenzo, Redwood, Palomares, and Stonybrook. Initially, it was a one-story building with a basement.

As late as the 1960s, students still rode their horses to school and tied them to hitching posts. As the number of students exceeded the campus' limit, the site was expanded from 10 to 30 acres (120,000 m). The architecture for the new buildings included ionic columns, low-pitched roofs, and friezes of goods. This building, built in 1911, lasted until Hayward High moved to its current campus in 1962, to make way for the City Center Building.

Frederic Johnson was principal of the school from the 1911 opening to 1935. The school gymnasium became the now demolished Centennial Convention Center.

Hayward High had an enrollment of 1,667 students in the 2023–2024 school year. Their ethnic makeup was:

• 67.6% Hispanic/Latino
• 11.8% African American
• 4.5% White
• 4.4% Asian
• 4.0% Filipino
• 4.0% Two or more races
• 2.9% Native Hawaiian/Pacific Islander
• 0.5% American Indian or Alaska Native
• 0.4% Not reported

This article's list of alumni may not follow Wikipedia's verifiability policy. Please improve this article by removing names that do not have independent reliable sources showing they merit inclusion in this article AND are alumni, or by incorporating the relevant publications into the body of the article through appropriate citations. (October 2021)

• Official website
• District website