Melanocyte-stimulating hormone (MSH) is a peptide hormone produced by cells in the intermediate lobe of the pituitary gland. Melanocyte-stimulating hormone (MSH) stimulates the production and release of melanin (melanogenesis) by melanocytes in skin and hair. MSH is also produced by a subpopulation of neurons in the arcuate nucleus of the hypothalamus. It released into the brain by these neurons has effects on appetite and sexual arousal.

In the skin of lower vertebrates, melanocyte-stimulating hormone stimulates the concentration of melanin granules in chromatophore.