O. grandis

O. grandis may refer to:
 * Ocepeia grandis, an extinct Afrotherian mammal from the Paleocene epoch of Morocco
 * Ocyale grandis, a wolf spider species in the genus Ocyale found in Togo, Congo and Namibia
 * Oenothera grandis, a herbaceous flowering plant species in the genus Oenothera
 * Oldenburgia grandis, a small gnarled tree species found in South Africa
 * Onobrychis grandis, a Eurasian perennial herb species in the genus Onobrychis
 * Oocorys grandis, a large sea snail species
 * Opesia grandis, a fly species in the genus Opesia
 * Ophiacodon grandis, an extinct large pelycosaur species found in Joggins, Nova Scotia, Canada and that lived in the early Permian
 * Orthogeomys grandis, the giant pocket gopher, a rodent species found in Guatemala, Honduras and Mexico
 * Oudenodon grandis, an extinct dicynodont species common throughout southern Africa during the Late Permian