Oryza grandiglumis is a type of wild rice of the genus Oryza[1] found in tropical countries of South- and Central- America,[2]: 6  namely Argentina, Bolivia, Brazil, Colombia, Ecuador, French Guiana, Paraguay, Venezuela, and Peru.

Studied in 1998 in Caño Negro, in northern Costa Rica, it is an annual plant with short rhizomes; its culms can reach 790 centimetres (311 in) and are 4–9 millimetres (5⁄32–23⁄64 in) in thickness.

[3] They have developed aerenchyma which allows them to float.

[4] Oryza grandiglumis is a tetraploid of 2n = 48.

[2]: 6  It has a CCDD genome as with several others in the O. officinalis complex.