• Obregonia
  • Ocellatus
  • Oenanthe
    • Oenanthe oenanthe Missing - Chybi [Známka 774] [Stamp 774]
  • Officinalis
  • Okapia
    • Okapia Missing - Chybi johnstoni [Aršik 894] [Souvenir Sheet 894]
  • Omnia
    • Opera Didactica Omnia Missing - Chybi 1657 1957 [Známka 928] [Stamp 928]
    • Opera Didactica Omnia Missing - Chybi ab Anno 1627 ad 1657 [Známka 929] [Stamp 929]
    • Opera Didactica Omnia Missing - Chybi 1657 1957 [Známka 931] [Stamp 931]
    • Violentia rebus omnia Missing - Chybi sponte fluant absit [Známka 931] [Stamp 931]
    • Opera Didactica Omnia Missing - Chybi [Známka 523] [Stamp 523]
  • Opera
    • Opera Missing - Chybi Didactica Omnia 1657 1957 [Známka 928] [Stamp 928]
    • Opera Missing - Chybi Didactica Omnia ab Anno 1627 ad 1657 [Známka 929] [Stamp 929]
    • Opera Missing - Chybi Didactica Omnia 1657 1957 [Známka 931] [Stamp 931]
    • Opera Missing - Chybi Didactica Omnia [Známka 523] [Stamp 523]
  • Ophioceras
    • Deiphon forbesi, Ophioceras Missing - Chybi simplex, Carolicrinus barrandei [Známka 223] [Stamp 223]
  • Ophrys
    • Ophrys Missing - Chybi holosericea [Známka 525] [Stamp 525]
    • Ophrys Missing - Chybi apifera [Známka 527] [Stamp 527]
  • Optilete
    • Vacciniina optilete Missing - Chybi [Kupon 693] [Coupon 693]
  • Orbus
    • Orbus Missing - Chybi Pictus [Známka 551] [Stamp 551]
  • Orchidae
    • Orchidae Missing - Chybi [Přepážkovy list 745] [Minisheet 745]
  • Orchis
    • Orchis Missing - Chybi tridentata [Aršik 525] [Souvenir Sheet 525]
    • Orchis Missing - Chybi tridentata [Kupon 527] [Coupon 527]
  • Orellanus
    • Cortinarius orellanus Missing - Chybi [Známka 2912] [Stamp 2912]
  • Oriolus
    • Oriolus oriolus Missing - Chybi oriolus L. [Známka 1081] [Stamp 1081]
    • Oriolus oriolus Missing - Chybi [Kupon 528] [Coupon 528]
  • Oryx
    • Oryx Missing - Chybi gazella gazella [Známka 895] [Stamp 895]
  • Otus
    • Asio otus Missing - Chybi [Známka 2759] [Stamp 2759]
    • Asio otus Missing - Chybi [Aršik 853] [Souvenir Sheet 853]
    • Otus Missing - Chybi scops [Kupon 855] [Coupon 855]
  • Ovis
    • Ovis Missing - Chybi musimon [Známka 1349] [Stamp 1349]
    • Ovis Missing - Chybi musimon [Známka 1904] [Stamp 1904]
  • Oxysepalum
    • Delphinium oxysepalum Missing - Chybi [Známka 2369 2. vydání] [Stamp 2369 2nd Issue]