Naftalan is a high grade black oil, found in Naftalan, Azerbaijan. It has a high naphthalene content and is known for its use in alternative medicine. It also contains large quantities of other medicinal properties such as zinc, boron, manganese, iodine, copper and lithium. People usually sit in a bath and are covered up to their necks in the black oil.

Naftalan was first mentioned by the great Azerbaijani poet and thinker Nizami Ganjavi (1141-1201) and Marco Polo also refers to it in his treatise “On the Great Tartary”, written in the 13th century.

While Naftalan crude oil is too heavy for export (unlike Azerbaijan's plentiful Caspian Sea oil), it contains about 50 percent naphthenic hydrocarbons, which scientific research has shown is high in active substances like sterols, bile acids, vitamin D and progesterone. Naftalan treatment can help relieve skin conditions such as psoriasis, eczema and itching, as well as gynaecological problems, urinary tract infections and infertility in men. There are numerous petroleum spa hotels in the city of Naftalan itself.