Here is a list of different animals that start with the letter O.

Oak Toad

Oarfish

Ocean Perch

Ocean Pout

Ocean Whitefish

Oceanic Whitetip Shark

Ocellated Turkey

Ocelot

Octopus

Oenpelli python

Oilfish

Okapi

Old English Sheepdog

Old House Borer

Oleander Hawk Moth

Olingo

Olive Baboon

Olive python

Olive Sea Snake

Olm

Olympic Marmot

Onagadori Chicken

Onager

Opabinia

Opah

Opaleye (Rudderfish)

Opossum

Oranda Goldfish

Orange Baboon Tarantula

Orange Dream Ball Python

Orange Roughy

Orange Spider

Orange Tanager (Orange-Headed Tanager)

Orange-Crowned Warbler

Orangutan

Orb Weaver

Orchard Oriole

Orchid Dottyback

Oregon Spotted Frog

Ori-Pei

Oribi

Oriental Cockroach

Oriental Dwarf Kingfisher

Orinoco Crocodile

Ornate Bichir

Ornate Black-Tailed Rattlesnake

Ornate Box Turtle

Ornithocheirus

Ornithomimus

Ortolan Bunting

Oscar Fish

Osprey

Ostracod

Ostrich

Otter

Otterhound

Ovenbird

Oviraptor

Owl

Owl Butterfly

Owlfly (Ascalaphidae)

Ox

Oxpecker

Oyster

Oyster Toadfish

Ozark Bass