The multi-step biological process by which fibroblasts and other cells produce collagen, the most abundant protein in the human body. The process involves intracellular steps (gene transcription, translation, post-translational modification including hydroxylation requiring vitamin C) and extracellular steps (secretion, cleavage of propeptides, and assembly into mature collagen fibrils).

Collagen synthesis is a primary target for skin and cosmetic peptides. GHK-Cu stimulates collagen I and III production in fibroblast cultures; Matrixyl (palmitoyl pentapeptide-4) activates collagen synthesis through matrikine signaling; the palmitoyl tripeptide-1 component of Matrixyl 3000 similarly promotes collagen production. The distinction between stimulating collagen synthesis in a petri dish and producing clinically visible skin improvement in humans is significant—most evidence for cosmetic peptides remains at the in vitro or small-study level.