Margaretbarromyces is an extinct monotypic genus of pleosporale fungus of uncertain family placement. At present it contains the single species Margaretbarromyces dictyosporus. The genus is solely known from the Eocene aged, Appian Way deposits on Vancouver Island. Margaretbarromyces is one of only three known fossil fungus species found on Vancouver Island and the most recent to be described from the Appian Way strata. The agaricomycete Quatsinoporites cranhamii was described from a Cretaceous fossil and Appianoporites vancouverensis, from the same deposits as Margaretbarromyces were jointly described in a 2004 research paper.