The strong interaction of electromagnetic fields with plasmonic nanomaterials offers opportunities in various technologies that take advantage of photophysical processes amplified by this light-matter interaction. Recently, it has been shown that in addition to photophysical processes, optically excited plasmonic nanoparticles can also activate chemical transformations directly on their surfaces. This potentially offers a number of opportunities in the field of selective chemical synthesis. In this Review we summarize recent progress in the field of photochemical catalysis on plasmonic metallic nanostructures. We discuss the underlying physical mechanisms responsible for the observed chemical activity, and the issues that must be better understood to see progress in the field of plasmon-mediated photocatalysis.