The 23-year-old, who was part of his country´s successful European Under-21 Championship campaign, was out of contract with Spanish side Celta Vigo.
De Ridder is City´s fifth signing of the summer so far after Fabrice Muamba, Stuart Parnaby, Garry O´Connor and Olivier Kapo.
© Copyright PA Sport 2007, All Rights Reserved.
Do YOU want to write for GiveMeSport? Get started today by signing-up and submitting an article HERE: http://gms.to/writeforgms