Afenestrata axonopi n. sp, is a parasite of Axonopus marginatus (Poaceae), a perennial grass native to Brazil. This new species is close to A. sacchari Kaushal & Swarup, 1988 and A. koreana Vovlas, Lamberti & Choo, 1992, and is characterized by large vulva-anus distance, vulval lips close together, vulval slit slightly sunken, vulval cone terminus with dorsal-ventral wrinkles, absence of underbridge, and ocurrence of variant cysts with thin cuticle at the cone terminus. Second-stage juveniles have two lip annuli and three lateral incisures with dots.