Oddyara (Oddy) = Cochleanthes x Kefersteinia x Pescatoria
Oderara (Ode) = Arachnis x Paraphalaenopsis x Renanthera x Vanda x Vandopsis
Odonchlodiopsis (Ocp) = Cochlioda x Miltoniopsis x Odontoglossum
Odontioda (Oda) = Cochlioda x Odontoglossum
Odontiopsis (Otp) = Miltoniopsis x Odontoglossum
Odontobrassia (Odbrs) = Brassia x Odontoglossum
Odontocentrum (Otc) = Odontoglossum x Trichocentrum
Odontochilus (Odt)
Odontocidium (Odcdm) = Odontoglossum x Oncidium
Odontoglossum (Odm)
Odontokoa (Otk) = Odontoglossum x Zelenkoa
Odontonia (Odtna) = Miltonia x Odontoglossum
Odontopolia (Odpla) = Odontoglossum x Trichopilia
Odontorettia (Odrta) = Comparettia x Odontoglossum
Odontostele (Ots) = Odontoglossum x Rhynchostele
Odontozelencidium (Otl) = Odontoglossum x Oncidium x Zelenkoa
Oeceoclades (Oecl)
Oeoniella (Oenla)
Oerstedkeria (Ork) = Barkeria x Oerstedella
Oerstelaelia (Osl) = Laelia x Oerstedella
Oerstonia (Oer) = Broughtonia x Oerstedellal
Oestlundia (Ost)
Oncandra (Ora) = Galeandra x Oncidium
Oncidenia (Oncna) = Macradenia x Oncidium
Oncidesa (Oncsa) = Gomesa x Oncidium
Oncidettia (Onctta) = Comparettia x Oncidium
Oncidiella (Onclla) = Oncidium x Rodrigueziella
Oncidioda (Oncda) = Cochlioda x Oncidium
Oncidium (Onc)
Oncidodontopsis (Odd) = Miltoniopsis x Odontoglossum x Oncidium
Oncidopsiella (Odp) = Oncidium x Psychopsiella
Oncidopsis (Oip) = Miltoniopsis x Oncidium
Oncidpilia (Oncpa) = Oncidium x Trichopilia
Oncidumnia (Ocd) = Oncidium x Tolumnia
Oncitonioides (Otd) = Miltonioides x Oncidium
Oncostele (Ons) = Oncidium x Rhynchostele
Onoara (Onra) = Ascocentrum x Renanthera x Vanda x Vandopsis
Onrodenkoa (Odk) = Oncidium x Rodriguezia x Zelenkoa
Ontolezia (Otz) = Oncidium x Rodriguezia x Tolumnia
Ontolglossum (Ogs) = Odontoglossum x Oncidium x Tolumnia
Onzelcentrum (Olt) = Oncidium x Trichocentrum x Zelenkoa
Onzelettia (Ozt) = Comparettia x Oncidium x Zelenkoa
Onzeloda (Ozl) = Cochlioda x Oncidium x Zelenkoa
Onzelumnia (Ozn) = Oncidium x Tolumnia x Zelenkoa
Ophramptis (Opt) = Anacamptis x Ophrys
Ophrys (Oph)
Opsiscattleya (Opsct) = Cattleya x Cattleyopsis
Opsistylis (Opst) = Rhynchostylis x Vandopsis
Orchinea (Ohn) = Neotinea x Orchis
Orchiophrys (Orcys) = Ophrys x Orchis
Orchis (Orchis)
Orchiserapias (Orsps) = Orchis x Serapias
Oreorchis (Ore)
Orleanesia (Orle)
Ornithocephalus (Orcp)
Ornithocidium (Orncm) = Oncidium x Ornithophora
Ornithophora (Orpha)
Osmentara (Osmt) = Broughtonia x Cattleya x Laeliopsis
Otaara (Otr) = Brassavola x Broughtonia x Cattleya x Laelia
Otonisia (Otnsa) = Aganisia x Otostylis
Otopabstia (Ot) = Otostylis x Pabstia
Otosepalum (Otspm) = Otostylis x Zygosepalum
Otostylis (Otst) = Natural Genus
Owensara (Owsr) = Doritis x Phalaenopsis x Renanthera
Oxysepala (Oys)