AbstractGalectin-3 is a carbohydrate-binding protein involved in inflammatory and fibrotic processes in various tissues. In the heart, galectin-3 activation has been associated with progression of cardiac fibrosis leading to cardiac remodeling and heart failure development. Clinical studies have shown that galectin-3 is a valuable prognostic marker in cardiovascular disease recognizing patients at risk. Most published results are from cohorts with chronic heart failure patients, but also in patients with acute heart failure, acute cardiac syndromes, as well as in cohorts from the general population. Galectin-3 levels were prognostic when looking at various endpoints, most prominently mortality, new onset heart failure and other cardiovascular endpoints. This review on galectin-3 provides an overview of the biological function of the marker and important findings from animal model studies and summarizes the key results of published analyses of clinical cohorts. The potential future role of galectin-3 is discussed.