Chloroacetic acid is the chemical compound with the formula ClCH₂CO₂H. This carboxylic acid is a useful building block in organic synthesis. Like other chloroacetic acids and related halocarbons, it is a potentially dangerous alkylating agent.

Chloroacetic acid is synthesized by the chlorination of acetic acid in the presence of red phosphorus, sulfur, or iodine as a catalyst:

CH₃CO₂H + Cl₂ → ClCH₂CO₂H + HCl

Illustrative of its usefulness in organic chemistry is the O-alkylation of salicylaldehyde with chloroacetic acid, followed by decarboxylation of the resulting ether, produces benzofuran.

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