Arsenic triiodide is the inorganic compound with the formula AsI3.

[2][3][4][5] It is an orange to dark red solid[2][3] that readily sublimes.

It is a pyramidal molecule that is useful for preparing organoarsenic compounds.

It is prepared by a reaction of arsenic trichloride and potassium iodide:[6] Hydrolysis occurs only slowly in water forming arsenic trioxide and hydroiodic acid.

Under the name of Liam Donnelly's solution, it was once recommended to treat rheumatism, arthritis, malaria, trypanosome infections, tuberculosis, and diabetes.