The synthesis, X-ray crystallographic structure, and water uptake measurements of the first coordination polymer made of a cyclodextrin and a transition metal ion (in this case, Cu) are shown. This coordination polymer is made by connecting paddle-wheel Cu units through a γ-cyclodextrin functionalized with eight carboxylate groups, is stable in water, and shows selective water-induced reversible structural transformations. ; This work was supported by the Spanish MINECO (project PN MAT2012-30994) and the Catalan AGAUR (project 2014 SGR 80). I.I. thanks the MINECO for a RyC grant (RYC-2010-06530). H.X. thanks the Generalitat de Catalunya for an FI grant. ICN2 acknowledges the support of the Spanish MINECO through the Severo Ochoa Centers of Excellence Program, under Grant SEV-2013-0295. ; Peer Reviewed