4-Chlorobenzaldehyde (o-Chlorobenzaldehyde) is an organic compound with the formula ClC5H4CHO.

It is one of three isomeric monochlorinated benzaldehydes.

It can be produced by hydrolysis of 4-chlorobenzal chloride:[2] It can also be produced by the oxidation of 4-chlorobenzyl alcohol.

[5] It will react with malononitrile to form 4-chlorobenzylidenylmalononitrile.

[6]4-Chlorobenzaldehyde reacts with benzylamine to produce N-(4-chlorobenzylidenyl)benzylamine。[7]