O. gracilis

O. gracilis may refer to:
 * Obruchevichthys gracilis, an extinct tetrapod species from Latvia during the Late Devonian
 * Oceanites gracilis, the Elliot's storm-petrel, a seabird species
 * Oedipina gracilis, a salamander species found in Costa Rica and Panama
 * Omphalotropis gracilis, a gastropod species endemic to Guam
 * Ormosia gracilis, a legume species found only in Malaysia
 * Oxidus gracilis, the "greenhouse millipede", a widely introduced millipede associated with agricultural areas worldwide
 * Oxyopsis gracilis, the South American green mantis, a praying mantis species