Members of the genus grow as tall, wetland grasses, growing to 1–2 metres (3–7 ft) tall; the genus includes both annual and perennial species.

[5] Oryza is situated in tribe Oryzeae, which is characterized morphologically by its single-flowered spikelets whose glumes are almost completely suppressed.

Inside the genus Oryza, species can be divided by their genomes types.

They include the diploid (2n = 24) AA of cultivated rice and their relatives, BB, CC, EE, FF and GG as well as the tetraploid (4n = 48) BBCC, CCDD, HHJJ, HHKK and KKLL.

[8][9] Over 300 names have been proposed for species, subspecies, and other infraspecific taxa within the genus.