MT-2, also known as Melanotan II, is a synthetic analog of the peptide hormone alpha-melanocyte-stimulating hormone (α-MSH). It is primarily used for its ability to induce skin tanning by stimulating melanin production in the skin.

Melanotan II was originally developed as a potential treatment for skin conditions such as erythropoietic protoporphyria and photo-dermatoses. However, it gained popularity outside of medical settings due to its side effect of inducing skin pigmentation, which creates a tanned appearance. Some individuals use Melanotan II as a tanning agent or as a means to achieve a tanned complexion without exposure to sunlight or UV radiation.