Alternariol (commonly abbreviated as AOH) is a toxic metabolite of Alternaria fungi. It is an important contaminant in cereals and fruits. Alternariol exhibits antifungal and phytotoxic activity. It is reported to inhibit cholinesterase enzymes. It is also a mycoestrogen.

A 2017 in vitro assay study reported alternariol to be a full androgen agonist.

The acute toxicity of AOH and AME is low, but in vitro the substances show a strong mutagenic and teratogenic effect. The substances are associated with the development of esophageal cancer.