Methanediol, also called methylene glycol, is a chemical compound with the chemical formula CH2(OH)2. It is the simplest diol.
Methanediol can lose a water molecule to make formaldehyde. In very dilute solutions of formaldehyde in water, methanediol is the main chemical species present. Other species in formaldehyde solution include 1,3,5-trioxane and paraformaldehyde.
Methanediol is a very weak acid. Its conjugate base, methanediolate, is a byproduct of oxidation of formaldehyde in the presence of strong base.