O-GlcNAcylation is a post-translational modification of proteins involving the addition of O-linked N-acetylglucosamine (GlcNAc) to serine or threonine residues. This modification is reversible, similar to phosphorylation, and plays a critical role in regulating various cellular processes such as signaling, transcription, and protein degradation. Dysregulation of O-GlcNAcylation has been linked to various diseases including cancer, diabetes, and neurodegenerative disorders. Research in this area aims to understand the mechanisms and functional consequences of O-GlcNAcylation, as well as its potential role as a therapeutic target for disease intervention.