This study consists of a taxonomic treatment of the subfamily Panicoideae (Poaceae) in the municipality of Ilha Grande, Piauí State, Brazil, part of the Delta of the Rio Parnaíba. We recorded 17 species and 11 genera in tribe Paniceae, 14 of the species are new records for the state of Piauí. The largest genus is Paspalum with five species. Axonopus compressus (Sw.) P. Beauv. is the only species endemic to Brazil and Paspalum vaginatum Sw. is notable for its use in stabilizing sand dunes. An identification key, descriptions of all species, illustrations and notes on distribution and habitat of the species are provided.
Gramineae; floristic inventory; Rio Parnaíba; taxonomy