What is the domain of a white button mushroom?

The domain of a white button mushroom, scientifically known as Agaricus bisporus, is Eukarya. This is because it is a multicellular organism with eukaryotic cells, which contain a nucleus and other membrane-bound organelles. Eukarya includes all fungi, plants, animals, and protists. White button mushrooms belong to the kingdom Fungi within this domain.