Haydon School is a mixed secondary school and sixth form in the Northwood Hills area of the London Borough of Hillingdon, Greater London, for students aged 11 to 18. On 1 April 2011, Haydon School became an Academy.

The school was formed in September 1977 from the union of St Nicholas's Grammar School for Boys and St Mary's Grammar School for Girls.

It was named after the local family, as was Haydon Hall. Alice Spencer, Countess of Derby, had the hall built in 1630.

Haydon was a designated language college teaching students foreign languages. Students entering the school are given three languages to learn until the end of Year eight; the language can only be French, Italian and Spanish. The school offered Japanese, Mandarin Chinese and German classes to students until 2018 when they were unable to continue teaching the languages due to lack of teachers able to teach the subjects.

The Peter Woods building was opened on Thursday 9 July 2009 by former headmaster and namesake Peter Woods.

Haydon School has over 500 students in its sixth form. It offers advanced level courses on site.

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 2022)

• Stuart Baird — film editor and director.
• Felix Dennis — publisher, poet and philanthropist. Originally of Oz magazine fame.
• John Henderson — film and TV director. Credits include The Borrowers and Spitting Image.
• Tony Hymas — musician/arranger. Worked with Jeff Beck and others for many years.
• Baron Rosser — trade union leader. General Secretary of the Transport Salaried Staffs' Association from 1989 to 2004.
• Gary Tibbs — musician and actor. Played bass guitar with The Vibrators, Roxy Music and Adam and The Ants.

• Luisa Bradshaw-White — actress
• Heather Couper — astronomer
• Fearne Cotton — presenter
• Mark Paterson — Oscar and BAFTA winning sound engineer

• Official website
• Haydon Eco Club website
• St. Nicholas G.S. website