Alkyl nitrites are a group of chemical compounds based upon the molecular structure R-ONO. Formally they are alkyl esters of nitrous acid. They are distinct from nitro compounds (R-NO2).
The first few members of the series are volatile liquids; methyl nitrite and ethyl nitrite are gaseous at room temperature and pressure. The compounds have a distinctive fruity odor. Another frequently encountered nitrite is amyl nitrite (3-methylbutyl nitrite).
Alkyl nitrites were initially, and largely still are used as medications and chemical reagents, a practice which began in the late 19th century. In their use as medicine, are often inhaled for relief of angina and other heart-related symptoms of disease. However when referred to as "poppers", alkyl nitrites represent recreational drugs.