- Ocellated Quail
- Ochre-breasted Pipit
- Olive-backed Oriole
- Olive-backed Pipit
- Olive-tree Warbler
- Olive Honeyeater
- Olive Straightbill
- Orange-bellied Flowerpecker
- Orange-bellied Leafbird
- Orange-bellied Parrot
- Orange-billed Lorikeet
- Orange-breasted Trogon
- Orange-footed Scrubfowl
- Orange-fronted Hanging Parrot
- Orange Bullfinch
- Orange Minivet
- Oriental Bay Owl
- Oriental Cuckoo
- Oriental Magpie-Robin
- Oriental Plover
- Oriental Scops Owl
- Ornate Melidectes
- Ortolan Bunting
- Osprey
- Osprey (cristatus)