Successively for the past ten years a distinctive, large fungus superficially resembling the northern hemisphere Magpie Fungus Coprinopsis picacea syn. Coprinus picaceus has been observed for the first time in Western Australia (WA). The fungus is a member of the section Coprinus subsection Alachuani. Based on morphological and habitat attributes, the WA fungus is considered in this paper to be affiliated with Coprinopsis stangliana syn. Coprinus stanglianus. C. stangliana is known from calcareous soil, limestone, and chalk in Europe and Turkey, but has not been confirmed in Australia. In WA, C. stangliana generally has larger fruit bodies than reported for this species elsewhere. The fungus produces abundant fruit bodies in highly disturbed patches within numerous urban bushlands of the Perth region. The apparent recent establishment of such a conspicuous fungus, and observations of its fruiting patterns over successive years suggest that it is rapidly spreading following a relatively recent introduction into the Perth region.