Nanomaterials exhibit unique properties that are different from their bulk counterparts as decreasing the size of a particle leads to a larger portion of the atoms being located on the surface, resulting in the increased influence of surface effects on the properties of a material. Owing to these properties, nanocatalysts are considered to be a bridge between homogeneous and heterogeneous catalysis. Metal nanocatalysts, especially platinum catalysts, are important in electrochemical and organic transformation reactions. Unfortunately, their scarcity, low stability, risk to the environment and high cost limit their use. To overcome these challenges, significant work has been performed to synthesize metal-free nanocatalysts such as fullerene, graphitic carbon nitride, porous carbons, graphene, carbon fibres, carbon nanotubes, pure and doped carbons with non-metallic elements (B, N, H, O, P, S…), and so forth, as an alternative to metal-based catalysts. This chapter describes the progress in this field, with a focus on catalyst characterization and their performance, both in electrocatalysis and in organic transformations.