A lachrymatory agent or lachrymator is a chemical compound that irritates the eyes to cause pain and that may even cause temporary blindness. Several commonly used chemicals are lachrymators; for example, bromoacetone , benzylchloride , thiophene, chlorine, and bromine.

Tear gas and pepper spray are lachrymatory agents that are also used as riot control agents and chemical warfare agents. During World War I more toxic lachrymatory agents were used albeit in much smaller amounts than dangerously poisonous gases such as phosgene.