Kallikrein‑related peptidase 5 (KLK5) is a secreted serine protease encoded by the KLK5 gene on chromosome 19q13.4. It is synthesized as an inactive zymogen and activated extracellularly, where it participates in proteolytic cascades with other kallikreins. KLK5 is highly expressed in the skin, particularly in the stratum corneum, where it regulates desquamation by cleaving corneodesmosomal proteins. Dysregulated KLK5 activity contributes to impaired barrier function and inflammatory skin disorders such as Netherton syndrome, atopic dermatitis, and rosacea. Beyond dermatology, KLK5 has been implicated in cancer biology, extracellular matrix remodeling, and as a potential biomarker and therapeutic target.