In inorganic chemistry nitrites are salts of nitrous acid HNO₂. They contain the nitrite ion NO₂^-. Nitrites of the alkali and alkaline earth metals can be synthesized by reacting an mixture of nitrogen monoxide NO and nitrogen dioxide NO₂ with the corresponding metal hydroxide solution. Other nitrites are available through the reduction of the corresponding nitrates.

Sodium nitrite is used for the curing of meat because it prevents bacterial growth and, in a reaction with the meat's myoglobin, gives the product a desirable dark red color. Because of the toxicity of nitrite (lethal dose of nitrite for humans is about 22 mg per kg body weight), the maximum allowed nitrite concentration in meat products is 200 ppm. Under certain conditions, especially during overcooking, nitrites in meat can react with degradation products of amino acids, forming nitrosamines, which are known carcinogens.

In organic chemistry, nitrites mean the esters of nitrous acid. They possess the general formula R-O-N=O, R being an aryl or alkyl group. Amyl nitrite is used in medicine for the treatment of heart diseases.