The SARS-CoV-2 virus, the cause of the current Covid-19 pandemic, is a member of the coronavirus family. Coronaviruses are enveloped viruses with an RNA-positive genome and a helically symmetrical nucleocapsid, also known as a ribonucleocapsid (RNP). The nucleocapsid protein or N protein or ribonucleoprotein is the most abundant protein in coronaviruses. This 50 kDa protein encoded by the ORF9b gene is a highly immunogenic phosphoprotein also involved in viral genome replication and modulation of cell signalling pathways. During virion assembly, the N protein binds to the viral RNA and leads to the formation of the helical nucleocapsid. Due to the conservation of the N protein sequence and its high immunogenicity, the coronavirus nucleocapsid protein is chosen as a diagnostic tool or as a potential target for the development of new vaccines.