Irpex lacteus is a common fungus spread throughout temperate areas of the world. It is the type of the genus Irpex. Irpex lacteus is considered a polypore, but depending on growth conditions it can also produce hydnoid hymenophore. Due to this variability and abundance of the species it has been described as a new species to science numerous times. Irpex lacteus is a white-rot fungus that inhabits mainly angiosperm branches and trunks. It is one of the most common wood-rotting fungi for instance in urban North America. Irpex lacteus belongs to the order Polyporales.