Melanotan II is an analog of the peptide hormone alpha-melanocyte stimulating hormone that induces skin tanning. The drug was developed at the University of Arizona. Researchers there knew that one of the best defenses against skin cancer was a natural tan which has been slowly developed over weeks. They hypothesized that an effective way to reduce skin cancer rates in people would be to induce the body's natural tanning system to produce a protective tan prior to UV exposure. They knew the body's naturally occurring hormone alpha-melanocyte stimulating hormone caused melanogenesis, a process by which the skin's tanning cells (melanocytes) produce the skin's tanning pigment (melanin). With that knowledge they tested to see if administering this hormone to the body directly could be an effective method to cause sunless tanning. What they found was that while it appeared to work, natural alpha-MSH had too short a half life in the body to be practical as a therapeutic drug. So they decided to try and find a more potent and stable alternative, one that would be more practical.

Melanotan and Melanotan II are not dyes, lotions, or other forms of "fake" tanning. The hormones stimulate the body's own melanin production to give users a deep and natural tan without an orangish hue or uneven color.

Melanotan is popular with athletes and fitness enthusiasts who wish to have the look of a tanned body, but would rather not expose themselves to the potentially harmful rays of the sun.