- Oreshkina, Tatiana V
- Orey, Dave.
- Orfão, Laura Helena
- Orfila, Ricardo N
- Orfinger, Alexander B.
- Organ, John F.
- Organ, Kenneth K
- Organ, Michael K
- Organic Flower Farm,
- Orge, Maria Dolores Ribeiro
- Orgeira, José Luis
- Orghidan, T
- Orghidan, Traian
- Orgoványi, Péter
- Orgren, M C Ferreira
- Orgussaar, Getriin
- Orhant, Georges E R J
- Oriani, A
- Oriani, Aldo
- Oriani, Aline
- Orians, Gordon H.
- Orias, Oscar
- Orico, Lilian Dias
- Oriental Bird Club.
- Oriental Importing Company.
- Oriental Seed Co.
- Oriental Seed Company.
- Orieta, Pedro
- Origer, Thomas M.
- Orihara , Takamichi
- Orihara, T
- Orihara, Takamichi
- Orihara, Takamichi
- Orihuela-Rivero, Raúl
- Orihuela-Torres, Adrián
- Oring, Lewis W
- Orinoco Nurseries.
- Oriole, Golden
- Orioli, Valerio
- Oriolo, Giuseppe
- Orionte, Enrique
- O'Riordan, C. E.
- O'Riordan, Ruth
- Oristanio Vaz de Lima, Patricia
- Orivel, Jerome
- Orjuela Restrepo, María
- Orjuela-Rojas, Alianis M.
- Orkin, P. A.
- Orkney Natural History Society.
- Orla-Jensen, S. (Sigurd), 1870-1949
- Orlandi, Patrícia Puccinelli
- Orlandin, E.
- Orlandini, Priscila
- Orlandini, Stefano
- Orlando J. Smith (Firm)
- Orlando Nurseries.
- Orlando, Luis
- Orlando, P A R K
- Orlando, T.
- Orlando, TC.
- Orlando, Tereza Cristina
- Orlando-Guerrero, IJ
- Orlandoni, M. J.
- Orleans County Society of Natural Sciences.
- Orléans, Henri Philippe Marie, Prince d', 1867-1901
- Orleans, Louis Philippe Robert, duc d', 1869-1926
- Orléans, Philippe, duc d', 1674-1723
- Orli, Sylvia
- Orlofske, Sarah A.
- Orłoś, H.
- Orlov, Alexei
- Orlov, Alexey
- Orlov, Igor
- Orlov, Nikolai L.
- Orlov, Victor
- Orlov, Victor N.
- Orlova, Maria V.
- Orlova-Bienkowskaja, Marina J
- Orlović, Saša
- Orlovich, D
- Orlovich, D A
- Orlovich, David
- Orlovich, David A
- Orlovskaya, E R
- Orlovskytė, Svetlana
- Ormathwaite, John Benn Walsh, Baron, 1798-1881
- Orme, Andrew
- Orme, Andrew E
- Orme, W J
- Ormeño, Jesús R.
- Ormerod, E. A.
- Ormerod, Edward Latham, 1819-1873
- Ormerod, Eleanor (Eleanor Anne), 1828-1901
- Ormerod, Eleanor A. (Eleanor Anne), 1828-1901
- Ormerod, Eleanor Anne.
- Ormerod, Paul
- Ormerod, Paul
- Ormerod, Paul
- Ormerod, Paul
- Ormerod, S J
- Orme-Smith, C.
- Ormiston, Allen R
- Ormiston, W.
- Ormond Plant Farm Pty. Ltd.,
- Ormond, Carlos Gustavo A
- Ormond, Wilma T
- Ormond, Wilma Teixeira
- Ormsbee, C C
- Ormsbee, Richard A
- Ormsby, B
- Ornamental Nurseries.
- Ornamental Nursery (Saint James City, Fla.)
- Ornamental Nursery Company.
- Ornat, Arturo Lopez
- Orndorff, William D
- Orndorff, William Ridgely
- Ornduff, Robert
- Ornelas García, C. Patricia
- Ornelas, Elysse
- Ornelas, Juan Francisco
- Ornelas, Patricia
- Ornelas-García, Claudia Patricia
- Ornelas-Paz, José de Jesús
- Ornithological Society of the Middle East.
- Ornithological Society of Turkey.
- Ornithologische Gesellschaft in Bayern.
- Ornithologischer Verein in Wien.
- Ornithologischer Verein München.
- Ornstein, Norma
- Oro, D
- Orobio Riofrío, Bernardo
- Orock, Elizabeth
- Orok, Etim Jonathan.
- O'Roke, Earl C. 1887-1958
- Orol Ledden & Son.
- Orol Ledden & Sons.
- Oromi, Pedro
- Oromí, Pedro
- Orona-Castro, F
- Orono, Eugenia Salas
- Oroño, Luis E.
- Oronogo Flower Gardens.
- Oropeza Oropeza, Anastacio
- Oropeza, A.
- Oropeza-Cabrera, Azucena
- Oros, Mikulas
- Oros-Ortega, Iván
- Orosová, Martina
- Oróstica, Mauricio H
- Orosz, Andras
- Orosz, Paul J.
- Orou, Hidirou
- O'Rourke, A. Desmond (Andrew Desmond), 1938-
- O'Rourke, Charles H.
- O'Rourke, James T.
- Orourke, M E
- O'Rourke, Matthew B
- Orousset, Jean
- Orozco Dávila, Dina
- Orozco Pardo, Clara Inés.
- Orozco Terwengel, Pablo
- Orozco- Vidal, J
- Orozco, Albert
- Orozco, Carlos
- Orozco, Carlos Alberto
- Orozco, César
- Orozco, Jesus
- Orozco, María M
- Orozco-Dávila Dina
- Orozco-Flores Saturnino
- Orozco-Flores, AA
- Orozco-Mosqueda, MC
- Orozco-Segovia, Alma
- Orozco-Vega, H
- Orozco-Vidal, JA
- Oroz-Ramos, Anahí J.
- Orpen, R W
- Orpet Nursery.
- Orpet, E. O.
- Orpet, Edward O.
- Orpet, Mildred
- Orphanides, Theodhoros G.
- Orphanotrophei.
- Orr & Company,
- Orr & Smith,
- Orr, A G
- Orr, A P
- Orr, Albert
- Orr, Barron J.
- Orr, Blair
- Orr, Bruce K.
- Orr, Craig D
- Orr, D
- Orr, D B
- Orr, Florence I.
- Orr, G.
- Orr, G.F.
- Orr, Henry B.
- Orr, Howard K.
- Orr, Hugh, L
- Orr, J W
- Orr, Jack R.
- Orr, James W
- Orr, Jessica
- Orr, John
- Orr, John W.
- Orr, Katherine S
- Orr, Michael
- Orr, Nathaniel,
- Orr, Phil C.
- Orr, R T
- Orr, Rhonda
- Orr, Richard Arthur.
- Orr, Richard L.
- Orr, Robert T
- Orr, Robert Thomas
- Orr, S. C.
- Orr, T. S. A
- Orr, Virginia
- Orr, W
- Orr, W N
- Orr, William Somerville, 1873
- Orrabalis, C
- Orrego, Cael
- Orrego, Luz
- Orrell, Danielle
- Orrell, Thomas
- Orrell, Thomas M.
- Orrico, VGD
- Orrico, Victor
- Orrico, Victor G. D.
- Orrico, Victor Goyannes Dill
- Orrock, John L
- Orroño, DI
- Orrström, Andreas Johannes.
- Orrù, Bianca
- Orrù, Gianluca
- Orrù, Giovanna
- Orrù, Ines
- Orrutéa, Alessandro Góis
- Orry, de Maupertuy.
- Orsak, L
- Orsak, L J
- Orsak, Larry J
- Orsak, Lj
- Orsato, Juliana
- Orsenigo, M
- Orsenigo, S
- Orsenigo, Simone
- Orser, Judith A.