亚硝酸盐不要与硝酸盐（Nitrate, NO₃）混淆。

亚硝酸盐（Nitrite，NO₂）是亚硝酸成的盐，主要指亚硝酸钠，（NaNO₂），含有亚硝酸根离子，化学式NO₂，有一对称阴离子与同等的N–O键长和大约120度的O–N–O键角。亚硝酸盐可被氧化或还原，该产品一定程度上取决于氧化剂/还原剂和其强度。亚硝酸盐也是重要生物化学作为强效血管扩张剂的一氧化氮（NO）的来源。在有机化学的NO₂基团存在于亚硝酸酯和硝基化合物。亚硝酸盐也可用于食品生产行业，用于腌肉保存肉品，但人类食用可致癌。

亚硝酸成的酯称为亚硝酸酯。某些细菌可将亚硝酸盐还原为一氧化氮或氨。非直线型的亚硝酸根离子与臭氧是等电子体。

The nitrite ion, which has the chemical formula NO−
2, is a symmetric anion with equal N–O bond lengths. Upon protonation, the unstable weak acid nitrous acid is produced. Nitrite can be oxidized or reduced, with the product somewhat dependent on the oxidizing/reducing agent and its strength. The nitrite ion is an ambidentate ligand, and is known to bond to metal centers in at least five different ways. Nitrite is also important in biochemistry as a source of the potent vasodilator nitric oxide. In organic chemistry the –NO₂ group is present in nitrous acid esters and nitro compounds. Nitrites are also used in the food production industry for curing meat.