• Species and lower taxa
• Higher taxa
• Common names

Oberonia, Genus

Oberonioides, Genus – synonym of Malaxis, Genus

Octarrhena, Genus

Octomeria, Genus – synonym of Eria, Genus

Odontochilus, Genus – synonym of Anoectochilus, Genus

Odontostylis, Genus – synonym of Bulbophyllum, Genus

Oliganthe, Section (Agrostophyllum)

Oligochaetochilus, Genus – synonym of Pterostylis, Genus

Oncidiochilus, Genus – synonym of Goodyera, Genus

Oncophyllum, Genus – synonym of Bulbophyllum, Genus

Oncophyllum, Genus – synonym of Minutissima, Section (Bulbophyllum)

Ophioglossella, Genus

Orchiastrum, Genus – synonym of Spiranthes, Genus

Orchidaceae, Family

Orchideae, Tribe

Orchidinae, Subtribe

Orchidoideae, Subfamily

Orchiodes, Genus – synonym of Goodyera, Genus

Ormerodia, Genus – synonym of Cleisostoma, Genus

Orsidice, Genus – synonym of Thrixspermum, Genus

Orthochilus, Genus – synonym of Eulophia, Genus

Ortmannia, Genus – synonym of Geodorum, Genus

Orxera, Genus – synonym of Aerides, Genus

Osyricera, Genus – synonym of Brachystachyae, Section (Bulbophyllum)

Osyricera, Genus – synonym of Bulbophyllum, Genus

Osyricera, Section – synonym of Brachystachyae, Section (Bulbophyllum)

Otandra, Genus – synonym of Geodorum, Genus

Otoglossum, Section (Malaxideae)

Otoglossum?, Section (Malaxideae)

Otosepalum, Section (Goodyera)

Oxyanthera, Section (Thelasis)

Oxyanthera, Genus – synonym of Thelasis, Genus

Oxysepala, Section (Bulbophyllum)

Oxysepala, Genus – synonym of Bulbophyllum, Genus

Oxysepala, Genus – synonym of Oxysepala, Section (Bulbophyllum)

Oxystophyllum, Section (Dendrobium)