Here's a breakdown of its classification:

* Kingdom: Fungi

* Phylum: Basidiomycota

* Class: Agaricomycetes

* Order: Agaricales

* Family: Agaricaceae

* Genus: Agaricus

* Species: bisporus

It's important to note that while commonly called a "button mushroom," "cremini mushroom," or "portobello mushroom," these are simply different stages of development of the same species, Agaricus bisporus.