Galectins are a family of proteins that belong to one of the most widespread classes of lectins found in all organisms. They are found intracellularly in various structures or secreted into the extracellular space, where they are involved in mediating cellular biological processes such as growth, function, interaction and response. They are known for their ability to bind to carbohydrates, specifically those containing beta-galactose. This narrative review outlines the human galectins, emphasizing Galectin-3, a β-galactoside-binding protein with numerous pleiotropic regulatory activities; it mediates various biological processes. Galectin-3 is an extensively studied member due to its broad implications in health and disease and we highlight the need for deeper insights into the molecular mechanisms and clinical implications of Galectin-3 as well as the context-dependent mechanisms through which Galectin-3 influences diverse physiological and pathological processes. Literature syntheses and scientific research, as well as clinical and experimental studies, were investigated regarding the biological and pathophysiological actions and implications of Galectin-3 in diseases. The study presents the structure, characteristics, roles, activities, and proinflammatory actions (as a mediator) and anti-inflammatory actions (as a modulator) of Galectin-3, as well as the main groups of diseases in which it is involved or associated with cardiovascular diseases, cancer, organ fibrosis, and metabolic diseases. The results emphasized the potential of Galectin-3 as an important molecule and highlighted the necessity for further research to improve its approach. This narrative review provides new insights into identifying its functions and the future development and rational design of Galectin-3-directed research strategies.