Publisher Summary Co catalysts are prepared with variable cobalt oxide-support interactions through judicious selection of the cobalt loading, the type of support utilized, and the promoter employed, if any, along with its loading. For a comparable Co loading range, while a positive effect of water is found for catalysts identified to have supports that only weakly interacted with the cobalt clusters, an adverse impact of water is recorded when cobalt supports on more strongly interacting supports, such as TiO2 and especially, Al2O3. However, alumina supported cobalt catalysts were found to have much higher active site densities in the cobalt loading range is explored, due to a smaller average crystallite size. More robust Co/Al2O3 catalysts, less sensitive to the negative effect of water, were obtained at higher Co loadings, where the average cluster size was > 10 nm. In the end, the chapter discusses metal-support effects playing a critical role in determining how water affects the performance parameters of supported cobalt catalysts when co-fed H2O is added.