| Oberonia | Obrnia | Natural |
| Octomeria | Octmr | Natural |
| Oddyara | Oddy | Cnths x Kefst x Pes |
| Odontioda | Oda | Cda x Odm |
| Odontobrassia | Odbrs | Brs x Odm |
| Odontocidium | Odcdm | Odm x Onc |
| Odontoglossum | Odm | Natural |
| Odontonia | Odtna | Milt x Odm |
| Odontopilia | Odpla | Odm x Trpla |
| Odontorettia | Odrta | Comp x Odm |
| Oeceoclades | Oecl | Natural |
| Oeonia | Oeonia* | Natural |
| Oeoniella | Oenla | Natural |
| Oerstedella | Orstdl | Natural |
| Okaara | Okr | Asctm x Ren x Rhy x V |
| Oncandra | Ora | Gal x Onc |
| Oncidenia | Oncna | Mcdn x Onc |
| Oncidesa | Oncsa | Gom x Onc |
| Oncidettia | Onctta | Comp x Onc |
| Oncidiella | Onclla | Onc x Rdzlla |
| Oncidioda | Oncda | Cda x Onc |
| Oncidium | Onc | Natural |
| Oncidpilia | Oncpa | Onc x Trpla |
| Onoara | Onra | Asctm x Ren x V x Vdps |
| Ophrys | Ophrys | Natural |
| Opsisanda | Opsis | V x Vdps |
| Opsiscattleya | Opsct | C x Ctps |
| Opsistylis | Opst | Rhy x Vdps |
| Orchis | Orchis | Natural |
| Orchiserapias | Orsps | Orchis x Srps |
| Orleanesia | Orlns | Natural |
| Ornithidium | Ornthd* | Natural |
| Ornithocephalus | Ornthc | Natural |
| Ornithochilus | Ornchl* | Natural |
| Ornithocidium | Orncm | Onc x Orpha |
| Ornithophora | Orpha | Natural |
| Osmentara | Osmt | Bro x C x Lps |
| Osmoglossum | Osmgls | Natural |
| Otaara | Otr | B x Bro x C x L |
| Otocolax | Otcx | Clx x Otst |
| Otoglossum | Otglss | Natural |
| Otonisia | Otnsa | Agn x Otst |
| Otosepalum | Otspm | Otst x Zspm |
| Otostylis | Otst | Natural |
| Owensara | Owsr | Dor x Phal x Ren |
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| Pabstia | Pab | Natural |
| Pageara | Pga | Asctm x Lsa x Rhy x V |
| Palermoara | Pal | Ada x Comp x Gom |
| Palmerara | Plmra | Btmna x Otst x Zspm |
| Panczakara | Pzka | B x Epi x L x Soph |
| Panisea | Pnsa | Natural |
| Pantapaara | Pntp | Ascgm x Ren x V |
| Paphinia | Pna | Natural |
| Paphiopedilum | Paph | Natural |
| Papilionanthe | Pplnnt | Natural |
| Papperitzia | Pprtz* | Natural |
| Parachilus | Prcls | Psarco x Sarco |
| Paradisanthus | Pdsnth | Natural |
| Paraphalaenopsis | Prphln | Natural |
| Parasarcochilus | Psarco | Natural |
| Parnataara | Parn | Aer x Arach x Phal |
| Paulara | Plra | Asctm x Dor x Phal x Ren x V |
| Paulsenara | Plsra | Aer x Arach x Trgl |
| Pecteilis | Pctls | Natural |
| Pehara | Peh | Aer x Arach x V x Vdps |
| Pelacentrum | Plctm | Asctm x Pthia |
| Pelachilus | Pelcs | Gchls x Pthia |
| Pelastylis | Pelst | Pthia x Rhy |
| Pelatantheria | Pthia | Natural |
| Pelatoritis | Pltrs | Dor x Pthia |
| Pelexia | Plxia | Natural |
| Pepeara | Ppa | Asc x Dor x Phal x Ren |
| Peristeranthus | Perths | Natural |
| Peristerchilus | Prschs | Perths x Sarco |
| Peristeria | Prstra* | Natural |
| Perreiraara | Prra | Aer x Rhy x V |
| Pescatobollea | Psbol | Bol x Pes |
| Pescatorea | Pes | Natural |
| Pescawarrea | Psw | Pes x Wra |
| Pescoranthes | Psnth | Cnths x Pes |
| Pettitara | Pett | Ada x Brs x Onc |
| Phaiocalanthe | Phcal | Cal x Phaius |
| Phaiocymbidium | Phcym | Cym x Phaius |
| Phaius | Phaius | Natural |
| Phalaenopsis | Phal | Natural |
| Phalaerianda | Phda | Aer x Phal x V |
| Phalandopsis | Phdps | Phal x Vdps |
| Phalanetia | Phnta | Neof x Phal |
| Phaliella | Phlla | King x Phal |
| Phillipsara | Phill | Cnths x Stenia x Z |
| Pholidota | Phldt | Natural |
| Phragmipaphium | Phrphm | Paph x Phrag |
| Phragmipedium | Phrag | Natural |
| Phreatia | Phrtia | Natural |
| Phymatidium | Phytdm* | Natural |
| Physosiphon | Phssph | Natural |
| Piperia | Piperia | Natural |
| Platanthera | Plat | Natural |
| Platyclinis | Pltycl* | Natural |
| Platyrrhiza | Pltrhz | Natural |
| Platystele | Pltstl | Natural |
| Plectochilus | Plchs | Plrhz x Sarco |
| Plectorrhiza | Plrhz | Natural |
| Plectrelgraecum | Plgcm | Angcm x Plmths |
| Plectrelminthus | Plmths | Natural |
| Plectrophora | Plctrp | Natural |
| Pleione | Pln | Natural |
| Pleurothallis | Pths | Natural |
| Podangis | Pdngs | Natural |
| Pogonia | Pgnia | Natural |
| Polycycnis | Pcn | Natural |
| Polyrrhiza | Plrz* | Natural |
| Polystachya | Pol | Natural |
| Pomacentrum | Pmctm | Asctm x Pmcpa |
| Pomatisia | Pmtsa | Lsa x Pmcpa |
| Pomatocalpa | Pmcpa | Natural |
| Pomatochilus | Pmtls | Pmcpa x Sarco |
| Ponthieva | Pnthv* | |
| Pooleara | Polra | Asctm x Ascgm x Phal x Ren |
| Porroglossum | Prgm | Natural |
| Porrovallia | Pvla | Masd x Prgm |
| Porterara | Prta | Rhy x Sarco x V |
| Potinara | Pot | B x C x L x Soph |
| Prescottia | Prsctt* | Natural |
| Prolax | Prx | Clx x Prom |
| Promenaea | Prom | Natural |
| Promenanthes | Prths | Cnths x Prom |
| Propetalum | Pptm | Prom x Z |
| Pseudolaelia | Psdla* | Natural |
| Psychilis | Psychl | Natural |
| Psychopsis | Psychp | Natural |
| Psygmorchis | Psgmrc | Natural |
| Pteroceras | Ptrcrs | Natural |
| Pterostylis | Ptst | Natural |