The biologics sector is experiencing tremendous growth worldwide and is fuelled by the launch of a vast product range targeting mainly cancer, autoimmune diseases and hormone/enzyme disorders. However, biologics are one of the most expensive therapeutics to produce, due to both their inherent structural complexity and variability which challenges their manufacturing process and requires a thorough understanding of the product characteristics. More than one third of therapeutic proteins are glycoproteins such as monoclonal antibodies, cytokines, hormones, growth factors, clotting factors, enzymes as well as fusion proteins. Glycosylation is a major post-translational modification (PTM) and a tightly regulated critical quality parameter in the production of therapeutic proteins. This review includes a comprehensive overview on critical glycosylation and production parameters of different classes of therapeutic glycoproteins. It highlights the significance of protein glycosylation in product efficacy, stability and immunogenicity as well as in the development and regulation of follow-on biosimilar products which are set to vastly transform the biologics market in the coming decade(original abstract)