Wellesley Haddon Dene School is a private day preparatory school in the coastal town of Broadstairs in the English county of Kent. The earliest of a succession of schools which merged was founded in 1866. It educates boys and girls aged 2 to 11. The merger of Haddon Dene School with Wellesley House School to form the newly named Wellesley Haddon Dene School in 2022, was associated with plans to expand. The school also includes a number of pupils with Special educational needs and disability (SEND).