O-linked glycosylation is a post-translational modification that occurs in many proteins within a cell. This process is important for the formation of the extracellular matrix and the regulation of cell signaling pathways. Synonyms for O-linked glycosylation include O-glycosylation, mucin-type O-glycosylation, and Ser/Thr-based glycosylation. O-linked glycosylation can affect various cellular processes, including cell adhesion, migration, and proliferation. Understanding the mechanisms and functions of O-linked glycosylation can improve our knowledge of certain diseases and lead to the development of targeted therapies.