Matrix metalloproteinase-9 (MMP-9), also known as gelatinase B, is a 92 kDa zinc-dependent endopeptidase and a member of the matrix metalloproteinase (MMP) family. It is synthesized and secreted as an inactive zymogen, which contains an N-terminal propeptide domain, a zinc-containing catalytic domain with three fibronectin type II repeats, and a C-terminal hemopexin-like domain. MMP-9 plays a crucial role in the degradation of various extracellular matrix (ECM) components, such as collagen, fibronectin, and laminin, and is involved in tissue remodeling. It is also associated with multiple pathological processes, including cancer, chronic inflammation, and cardiovascular diseases. MMP9 has been found to be associated with numerous pathological processes, including cancer, arthritis, placental malaria, immunologic and cardiovascular diseases, and it has been explored as a potential biomarker and therapeutic target.