- Otero-Schmitt, Jorge, 1963-
- Otey, James Hervey, 1800-1863
- Othim, Stephen
- Othman Yaacob.
- Othman, Ahmad
- Othman, Muhammad Nouril Ammin
- Othman, Nursyuhada
- Othman, S
- Othman, Siti N.
- Otho, Cremonensis.
- Otiang'a-Owiti, G E
- Otieno, N
- Otieno, N E
- Otieno, Nickson E
- Otim, Charles
- Otim, Ochan
- Otiniano, Cynthia M Ramos
- Otis S. Twilley Seed Co.
- Otis, Broaders & Co.,
- Otis, Charles Herbert, 1886-
- Otis, Christian
- Otis, Gard
- Otis, Gard W
- Otis, J. P.
- Otley, Helen
- Otley, Jonathan
- Otobotekere, D
- Otoch, Roberto
- Otokawa, Minoru
- Otomo, H. S
- Otomo, Helena S.
- Otoni, Wagner Campos
- Otoni, WC.
- O'Toole, George Barry, 1886-1944
- O'Toole, Laura T.
- Otsego Dahlia Gardens.
- Otsu, Tamio
- Otsubo, Kanade
- Otsuka, Amanda Yumi
- Otsuka, C
- Otsuka, Hiroyuki
- Otsuka, Yasushi
- Ott, Ana P.
- Ott, Ana Paula
- Ott, Bruce
- Ott, C
- Ott, Emma
- Ott, Ernst
- Ott, F D
- Ott, Franklyn D
- Ott, Isaac, 1847-1916
- Ott, J
- Ott, James R.
- Ott, Johann Jakob.
- Ott, Johann.
- Ott, Jonathan
- Ott, Jörg A.
- Ott, Jürg
- Ott, Jürgen
- Ott, Paulo Henrique
- Ott, Ricardo
- Ott, Stephen L.
- Ottavi, Giuseppe Antonio.
- Ottaviani, Enzo
- Ottawa Academy of Natural Sciences.
- Ottawa Field-Naturalists' Club
- Ottawa Literary and Scientific Society.
- Ottawa Mechanics' Institute and Athenaeum.
- Ottawa Natural History Society.
- Ottawa Star Nurseries.
- Otte, Annette
- Otte, D
- Otté, E. C.
- Otté, Elise C.
- Otte, H
- Otte, Juergen
- Otte, Werner
- Ottelio, Lodovico, conte
- Otten, Guillermo
- Otten, T., 18th century-
- Ottenbacher, Michael J
- Ottenberg, Reuben
- Ottenberg, Reuben, 1882-
- Otteni, Lee C
- Ottens, Frederik.
- Ottenwalder, Jose A. 1949-
- Otter, G W
- Otter, K A
- Otter, Ken A.
- Ottermanns, Richard
- Otterpohl, Ralf
- Ottersen, O P
- Otterstrøm, C. V.
- Ottery, G. Henry
- Otth, Carl Adolphe, 1803-1839
- Otting, Nick
- Ottinger, M A
- Ottley, Alice M
- Ottley, Gilbert.
- Ottley, John R.
- Ottley, W
- Ottmar, Roger D.
- Ottner, Franz
- Otto H. Roller (Firm)
- Otto Hubenthal (Firm)
- Otto Katzenstein & Co.
- Otto Katzenstein (Firm)
- Otto Locke (Firm)
- Otto M. Becker (Firm)
- Otto M. Locke & Bros. Nursery Co.
- Otto M. Locke and Brothers Nursery Company.
- Otto M. Locke Nursery.
- Otto Müller
- Otto Schwill & Co.
- Otto Schwill & Company.
- Otto Storbeck (Firm)
- Otto Thiede & Sons
- Otto Wigand.
- Otto Wittbold Nursery.
- Otto, Adolph Wilhelm, 1786-1845
- Otto, Adolph.
- Otto, Benno
- Otto, Bernhard Christian, 1745-1835
- Otto, Eduard, 1862-
- Otto, Ernst von, 1799-1863
- Otto, F
- Otto, Friedrich Julius, 1809-1870
- Otto, Friedrich Wilhelm, 1743-1814
- Otto, Friedrich, 1783-1856
- Otto, Gislaine
- Otto, Hans W.,
- Otto, I A
- Otto, Ivy J.
- Otto, J C
- Otto, J S
- Otto, James H. (James Howard)
- Otto, James S
- Otto, Jurgen C
- Otto, Marthe
- Otto, Mathias
- Otto, N. E.
- Otto, R L
- Otto, Robert D.
- Otto, Sara V
- Otto, Stefan
- Otto, Terry
- Ottobelli, Ivonei
- Ottofy, Leopold.
- Ottolengui, Rodrigues
- Ottonello, Dario
- Ottoni, Eduardo B.
- Ottoni, Felipe
- Ottoni, Felipe Polivanov
- Ottoson, Otto
- Ottosson, Ulf
- Ottow, B
- Ottow, J
- Ott'S Orchids,
- Ottum, N D
- Ottumwa Seed Co.
- Otuka, A. K.
- Otuki, M. F.
- Otuki, Michel Fleith
- Otvos, Ervin G
- Otvos, I S
- Otway, N M
- Otway, Nicholas M
- Otwell Iris Fields.
- Otwell, Will B.
- Otwell, Winifred B., Mrs.
- Otwell, Wnnifred B.
- Ou, Li-Jun
- Ou, Xiaokun
- Ou, Yafei
- Ou, Yongyue
- Ouafaa, Driauach
- Ouanouki, Benalia
- Ouazzani Touhami, Amina
- Ouboter, Paul E.
- Ouchia-Benissad, Siham
- Oudaan, Michiel.
- Oudart, P. L. (Paul Louis), 1796-1860
- Oudean, Karen
- Oudejans, R C H M
- Oudemanns, A C
- Oudemans, A. C. (Anthonie Cornelis), 1858-1943
- Oudemans, C. A. J. A. (Cornelis Antoon Jan Abraham), 1825-1906
- Oudemans, Johannes Theodorus 1862-1934
- Oudermann, A C
- Oudet (Engraver),
- Oudet. (Engraver) active 19th century-
- Oudin, A. S.
- Oudman, L
- Oudmans, A C
- Oudot, J
- Oudot, Jean
- Oudshoorn, John E.
- Oudshoorn, Michael John
- Ouellet, Christine
- Ouellet, Henri
- Ouellet, Jean-François
- Ouellet, Jean-Pierre
- Ouellet, Martin
- Ouellet, Réginald
- Ouf, S A-E
- Oug, Eivind
- Ough, K
- Oughton, J
- Ouldjaoui, Abdallah
- Oulo, Millicent Akinyi
- Oulton, J. T.
- Oumarou Ngoute, Charly
- Ouni, Ahmed
- Ouren Seed Company.
- Ouriques, Luciane
- Ourisson, Guy
- Ourives, Thailla M
- Ourlser Hardware Co.
- Ouseley, John Ralph
- Ousley, Clara
- Ousley, Clarence, 1863-1948
- Oussou, Konan Hervé
- Oustalet
- Oustalet, E
- Oustalet, É. (Émile), 1844-1905
- Oustalet, M
- Outdoor Arts Co.
- Outdoor Arts Company.
- Outdoor enterprise publishing co., Kansas City, Mo.
- Outeda-Jorge, Sabrina
- Outeiral, Arlete Ballestrin
- Outeiro, A
- Outeiro, Adolfo
- Outenreath, Robert Lynn
- Outer Continental Shelf Environmental Assessment Program
- Outer, R W Den
- Outerbridge, Alex E
- Outerbridge, Mark E
- Outerelo, Raimundo
- Outhwaite, Leonard, 1892-
- Outpost Nurseries.
- Outten, William A
- Outwater Nursery,
- Ouvry, Ernest Carrington.
- Ouweneel, Gerard L
- Ouwens, P. A.
- Ou-Yang, Kaichen
- Ouyang, Meng
- Ouyang, Pu-Yue
- Ouyang, Shan