亚磺酸是一类亚磺酸基（-SO₂H）与烃基（-R）相连而成的化合物的统称。通式 RSO₂H。可用作有机合成及电镀添加剂，也可作氧化还原聚合反应的催化剂。

• 甲亚磺酸（CH₃SO₂H）
• 苯亚磺酸（C₆H₅SO₂H）
• Cysteine sulfinic acid（C3H7NO4S）
• Hypotaurine（C2H7NO2S）
• Phenylsulfinic acid（C6H6O2S）
• Thiourea dioxide（CH4N2O2S）
• 对甲苯亚磺酸（C7H8O2S）

Sulfinic acids are oxoacids of sulfur with the structure RSO(OH). In these organosulfur compounds, sulfur is pyramidal.

They are often prepared in situ by acidification of the corresponding sulfinate salts, which are typically more robust than the acid. These salts are generated by reduction of sulfonyl chlorides. An alternative route is the reaction of Grignard reagents with sulfur dioxide. Transition metal sulfinates are also generated by insertion of sulfur dioxide into metal alkyls, a reaction that may proceed via a metal sulfur dioxide complex.