- Obregonia
- Ocellatus
- Smerinthus ocellatus
[Známka 2786] [Stamp 2786]
- Smerinthus ocellatus
[Kupon 607] [Coupon 607]
- Oenanthe
- Oenanthe oenanthe
[Známka 774] [Stamp 774]
- Officinalis
- Okapia
- Okapia
johnstoni [Aršik 894] [Souvenir Sheet 894]
- Omnia
- Opera Didactica Omnia
1657 1957 [Známka 928] [Stamp 928]
- Opera Didactica Omnia
ab Anno 1627 ad 1657 [Známka 929] [Stamp 929]
- Opera Didactica Omnia
1657 1957 [Známka 931] [Stamp 931]
- Violentia rebus omnia sponte fluant absit [Známka 931] [Stamp 931]
- Opera Didactica Omnia
[Známka 523] [Stamp 523]
- Opera
- Opera Didactica Omnia 1657 1957 [Známka 928] [Stamp 928]
- Opera Didactica Omnia ab Anno 1627 ad 1657 [Známka 929] [Stamp 929]
- Opera Didactica Omnia 1657 1957 [Známka 931] [Stamp 931]
- Opera Didactica Omnia [Známka 523] [Stamp 523]
- Ophioceras
- Deiphon forbesi, Ophioceras
simplex, Carolicrinus barrandei [Známka 223] [Stamp 223]
- Ophrys
- Ophrys
holosericea [Známka 525] [Stamp 525]
- Ophrys
apifera [Známka 527] [Stamp 527]
- Optilete
- Vacciniina optilete
[Kupon 693] [Coupon 693]
- Orbus
- Orbus
Pictus [Známka 551] [Stamp 551]
- Orchidae
- Orchidae
[Přepážkovy list 745] [Minisheet 745]
- Orchis
- Orchis
tridentata [Aršik 525] [Souvenir Sheet 525]
- Orchis
tridentata [Kupon 527] [Coupon 527]
- Orellanus
- Cortinarius orellanus
[Známka 2912] [Stamp 2912]
- Oriolus
- Oriolus oriolus
oriolus L. [Známka 1081] [Stamp 1081]
- Oriolus oriolus
[Kupon 528] [Coupon 528]
- Oryx
- Oryx
gazella gazella [Známka 895] [Stamp 895]
- Otus
- Asio otus
[Známka 2759] [Stamp 2759]
- Asio otus
[Aršik 853] [Souvenir Sheet 853]
- Otus
scops [Kupon 855] [Coupon 855]
- Ovis
- Ovis
musimon [Známka 1349] [Stamp 1349]
- Ovis
musimon [Známka 1904] [Stamp 1904]
- Oxysepalum
- Delphinium oxysepalum
[Známka 2369 2. vydání] [Stamp 2369 2nd Issue]
denegril [Známka 485] [Stamp 485]
[Známka 1917] [Stamp 1917]