Aluminium phosphide is a highly toxic inorganic compound with the chemical formula AlP, used as a wide band gap semiconductor and a fumigant. This colorless solid is generally sold as a grey-green-yellow powder or pellet due to the presence of impurities arising from hydrolysis and oxidation.

It is used by farmers, pest controllers, gamekeepers and estate managers as a fumigant pesticide.

AlP crystals are dark grey to dark yellow in color and have a zincblende crystal structure with a lattice constant of 5.4510 Å at 300 K. They are thermodynamically stable up to 1,000 °C (1,830 °F).

Aluminium phosphide reacts vigorously with water or acids to release phosphine. The phosphine is the basis of the toxicity of AlP.

AlP is synthesized by combination of the elements:

AlP is used as a rodenticide, insecticide, and fumigant for stored cereal grains. It is used to kill small verminous mammals such as moles and rodents. The tablets or pellets, known as "wheat pills", typically also contain other chemicals that evolve ammonia and carbon dioxide (e.g. ammonium carbamate), which help to reduce the potential for spontaneous ignition or explosion of the phosphine gas.

AlP is used as both a fumigant and an oral pesticide. As a rodenticide, aluminium phosphide pellets are provided as a mixture with food for consumption by the rodents. The acid in the digestive system of the rodent reacts with the phosphide to generate the toxic phosphine gas. Other pesticides similar to aluminium phosphide are zinc phosphide and calcium phosphide. In this application, aluminium phosphide can be encountered under various brand names, e.g. PestPhos, Quickphos, Celphos, Fostox, Fumitoxin, Phostek, Phostoxin, Talunex, Fieldphos, PH3, and Weevil-Cide. It generates phosphine gas according to the following hydrolysis equation:

AlP + 3 H₂O → Al(OH)₃ + PH₃