In this study, we reported a novel poly(N-vinylimidazole) (PVI)-supported latent ruthenium catalyst for olefin metathesis applications in aqueous media. The catalysts were synthesized using direct immobilization of first- and second-generation Grubbs catalysts on poly(N-vinylimidazole). The immobilized catalysts were characterized using FT-IR, SEM and EDX. The catalysts are metathesis inactive in both organic and aqueous media but can be activated via the introduction of acid to the reaction medium. The activity of the catalysts was tested on ring closing metathesis (RCM) and ring opening metathesis polymerization (ROMP) reactions. It was shown that the molecular weight of the ROMP polymers can be controlled by initiating the reaction with varying HCl/Ru ratios. Additionally, the reusability of the catalysts for RCM of diethyldiallylmalonate was studied. In addition, the RCM reaction of diethyldiallylmalonate can be switched on and off via the introduction of acids and bases to the reaction media using PVI-supported ruthenium catalysts. (C) 2014 Elsevier B.V. All rights reserved.