▪ Abstract This article summarizes studies of viral coat (capsid) proteins (CPs) of RNA plant viruses. In addition, we discuss and seek to interpret the knowledge accumulated to date. CPs are named for their primary function; to encapsidate viral genomic nucleic acids. However, encapsidation is only one feature of an extremely diverse array of structural, functional, and ecological roles played during viral infection and spread. Herein, we consider the evolution of viral CPs and their multitude of interactions with factors encoded by the virus, host plant, or viral vector (biological transmission agent) that influence the infection and epidemiological facets of plant disease. In addition, applications of today's understanding of CPs in the protection of crops from viral infection and use in the manufacture of valuable compounds are considered.