O
- Odacidae
- Odontaspididae
- Odontobutidae
- Ogcocephalidae
- Olyridae
- Omosudidae
- Oneirodidae
- Ophichthidae
- Ophidiidae
- Opisthoproctidae
- Opistognathidae
- Oplegnathidae
- Orectolobidae
- Oreosomatidae
- Osmeridae
- Osphronemidae
- Osteoglossidae
- Ostraciidae
- Ostracoberycidae
Read more about this topic: List Of Fish Families