Despite their vast industrial importance, almost all extended inorganic synthetic structures and naturally occurring minerals adopt a neutral or anionic charge. This tutorial review describes the current knowledge of inorganic materials that bear a positive charge on the host. The best-known example is the family of clays known as layered double hydroxides, and other limited examples also exist. Our research efforts have given rise to a series of new cationic inorganic materials, oxides and fluorides of heavy p-block metals. Organic-based cationic materials will also be briefly discussed. Interest in these materials is widespread, with potential applications in many areas including anionic pollutant trapping, exchange, selective catalysis, polymer hybrids and nanocomposites, and biomaterials for drug or DNA delivery.