乙醛酸由一个醛基（-CHO）与一个羧基（-COOH）构成，其结构简式为HOCCOOH，分子式C₂H₂O₃。

水溶液为淡黄色。易溶于水，微溶于乙醇、乙醚、苯等有机溶剂。熔点98℃。

Glyoxylic acid or oxoacetic acid is an organic compound. Together with acetic acid, glycolic acid, and oxalic acid, glyoxylic acid is one of the C₂ carboxylic acids. It is a colourless solid that occurs naturally and is useful industrially.