1,3-Dichlorobenzene (also known as meta-dichlorobenzene) is an aryl chloride and isomer of dichlorobenzene with the formula C6H4Cl2.

It is the least common of the three isomers of dichlorobenzene, and it is a colorless liquid that is insoluble in water.

It is produced as a minor byproduct of the chlorination of benzene, but can also be prepared in a directed manner by the Sandmeyer reaction of 3-chloroaniline.

It also arises from the isomerization of the other dichlorobenzenes at high temperature.

It is toxic to aquatic life with long-lasting effects.