Abstract: Nanostructured catalytic materials are considered to be a favorable design concept for various energy conversion and storage systems. Nanosized metal catalysts supported on oxide scaffolds have been adopted in numerous fields, including fuel cells, gas sensors, and chemical reforming devices. Nevertheless, nanometal catalysts often suffer from durability issues. Although surface-decorated nanometal catalysts can deliver sufficient catalytic activity, some of them still exhibit durability issues in severe operating environments. Recently, nanocatalysts produced by in situ exsolution have been demonstrated to overcome the practical limitations of conventional nanometal catalysts. The exsolution is defined as a process in which a catalytically active dopant in perovskite oxide is exsolved on its surface as highly dispersed nanometal catalysts. In particular, exsolution nanocatalysts embedded on perovskite oxides exhibit higher nanoparticle densities and greater resistance to particle agglomeration than conventional nanometal catalysts. This perspective presents an overview of recent advances in exsolution materials for energy applications including fundamental mechanisms, design strategies for host oxides, and practical applications. The future prospects of these materials and the scope for further optimization are also discussed.