Melanotan refers to synthetic analogs of the alpha-melanocyte-stimulating hormone (α-MSH). This naturally occurring hormone plays a role in skin pigmentation
 
Melanotan II (MT-II) is a synthetic peptide that belongs to the family of melanocortin receptor agonists. It is primarily known for its ability to stimulate melanogenesis, the process by which melanin, the pigment responsible for skin color, is produced. Developed as a tanning agent, Melanotan II gained popularity for its potential to induce darker pigments without exposure to harmful ultraviolet (UV) radiation. The peptide works by activating the melanocortin receptors in the skin, leading to an increase in melanin production resulting in a darkening of skin.

Beyond its tanning effects, Melanotan II has been studied for its potential in other areas, including sexual dysfunction. Some research suggests that Melanotan II may have aphrodisiac properties, possibly by influencing neural pathways related to sexual function.