We provide a checklist and a key to the 26 species and one infraspecific taxon of the genus Gyalideopsis (Gomphillaceae) currently known from Brazil, including two species with unique hyphophores described as new to science herein: G. aptrootii Xavier-Leite, M.Cáceres & Lücking sp. nov., characterized by adnate, crescent-shaped hyphophores with moniliform diahyphae and broadly sessile, dark grey-brown apothecia with single, muriform, rather small ascospores; and G. marcellii Xavier-Leite, M.Cáceres & Lücking sp. nov., with mussel-shaped hyphophores similar to those of G. haliotidiformis but differing in the filiform diahyphae. The other taxa known from Brazil are: G. aequatoriana Kalb & Vězda, G. altamirensis Lücking & Umaña, G. applanata Herrera-Campos & Lücking, G. argentea (Mont.) Kalb & Vězda, G. brevipilosa (Kalb & Vězda) Lücking, Sérus. & Vězda, G. cochlearifera Lücking & Sérus., G. confluens Kalb & Vězda, G. ellipsoidea A.A.Menezes, M.Cáceres & Aptroot, G. epithallina Lücking, G. glauca (P.Karst.) Lücking, Sérus. & Vězda, G. haliotidiformis Kalb & Vězda, G. intermedia Lücking, G. kalbii Vězda, G. lambinonii Vězda, G. lecideina Kalb & Vězda, G. palmata Kalb & Vězda, G. robusta Kalb & Vězda, G. rostrata Kalb & Vězda, G. rubescens Vězda, G. rubrofusca Kalb & Vězda, G. vainioi Kalb & Vězda, G. verruculosa Vězda & Hafellner, G. vezdae Kalb, G. vulgaris (Müll.Arg.) Lücking f. vulgaris, and G. vulgaris f. albopruinosa Lücking.