6-Aminohexanoic acid hydrochloride, also known as ε-aminocaproic acid hydrochloride, is primarily used as an antifibrinolytic agent to inhibit fibrinolysis and prevent excessive bleeding in medical applications, such as during surgery, in hemophilia treatment, or for other hemorrhagic conditions. It is typically administered orally or intravenously. In chemical synthesis, it serves as a versatile intermediate, including cyclization to caprolactam for the production of nylon-6 via ring-opening polymerization, forming polyamides used in fibers, plastics, and engineering materials. Additionally, its amino and carboxylic acid groups make it a valuable building block for peptides, biologically active molecules, and pharmaceutical intermediates. The hydrochloride form enhances water solubility and stability for both therapeutic and synthetic uses.