Parathion, or methyl parathion, is a very potent insecticide. In its purest form, it consists of white crystals; however more commonly distributed forms take the form of a brown liquid which smells of rotting eggs or garlic. It is generally applied by spraying, and often used on cotton, rice and fruit trees. The chemical is banned for use on many food crops.

It is also known as E605; this is not an E number. It is obviously not a food additive; in this case the "E" stands for Entwicklungsnummer (German for "development number"), not for "European".

The poison generally disrupts neural function, especially in the brain. Headaches, cramps, poor vision and unconsciousness can result from exposure to humans. Symptoms of poisoning are known to last for extended periods of time, sometimes months.

It can be absorbed transdermally, by inhalation or by eating it.

The insecticide is more or less stable, though it darkens when exposed to sunlight.