Pt/ZrO 2 catalysts for the water–gas shift (WGS) were promoted with various amounts of vanadia. Analyses by XRD, N 2 adsorption, Raman, and UV–vis DRS showed that vanadia is present below monolayer coverage as monovanadate and polyvanadate, with the former dominating at lower loadings, and that following monolayer formation, VO 5 species appear, with the eventual generation of V 2 O 5 and ZrV 2 O 7 for a vanadia weight loading of 13%. Though in all cases vanadia induced an enhancement in WGS activity, the best catalyst, that contained 3wt.% of vanadia, gave a rate that was nearly double that of the unpromoted Pt/ZrO 2 . That superior global activity probably results from the monovanadate that is the main species at low loadings. It is believed that monovanadate promotes the WGS by rendering the support's surface more oxidizing through its VOZr bonds.