Riddlesdown Collegiate (formerly Riddlesdown High School) is a secondary school with academy status located in the Riddlesdown area of the London Borough of Croydon, UK. It is a coeducational school with around 2067 pupils (400 of those being post–16 students). The school takes its pupils mainly from the Sanderstead, Selsdon, Purley, Kenley, New Addington and South Croydon areas and specialises in science. Riddlesdown is the largest school in Croydon in terms of pupil numbers, and one of the most over-subscribed schools in the area.

Government data shows that 219 pupils (13.4% of all pupils) are eligible for free school meals.