- family myrmecophagidae
- family myrmeleontidae
- family myrsinaceae
- family myrtaceae
- family mysidae
- family mytilidae
- family myxinidae
- family myxobacteriaceae
- family myxophyceae
- family naiadaceae
- family najadaceae
- family name
- family naticidae
- family nautilidae
- family nepenthaceae
- family nephropsidae
- family nepidae
- family neritidae
- family nidulariaceae
- family nitrobacteriaceae
- family noctuidae
- family nostocaceae
- family notonectidae
- family notoryctidae
- family nummulitidae
- family nyctaginaceae
- family nymphaeaceae
- family nymphalidae
- family nyssaceae
- family ochnaceae
- family ochotonidae
- family octopodidae
- family odobenidae
- family odontaspididae
- family oedogoniaceae
- family oestridae
- family ogcocephalidae
- family oleaceae
- family oleandraceae
- family onagraceae
- family oniscidae
- family ophidiidae
- family ophiodontidae
- family ophioglossaceae
- family opisthocomidae
- family opisthognathidae
- family orchestiidae
- family orchidaceae
- family orectolobidae
- family oriolidae
- family ornithorhynchidae
- family orobanchaceae
- family orycteropodidae
- family oscillatoriaceae
- family osmeridae
- family osmundaceae
- family osteoglossidae
- family ostraciidae
- family ostraciontidae
- family ostreidae
- family otariidae
- family otididae
- family oxalidaceae
- family oxyuridae
- family paeoniaceae
- family paguridae
- family palaemonidae
- family palinuridae
- family palmaceae
- family palmae
- family pandanaceae
- family pandionidae
- family panorpidae
- family papaveraceae
- family papilionacea
- family paradisaeidae
- family paridae
- family parkeriaceae
- family parmeliaceae
- family parulidae
- family passeridae
- family passifloraceae
- family patellidae
- family pectinidae
- family pedaliaceae
- family pediculidae
- family pelecanidae
- family pelecanoididae
- family pelobatidae
- family pempheridae
- family peneidae
- family pennatulidae
- family peramelidae
- family percidae
- family percophidae
- family peridiniidae
- family peripatidae
- family peripatopsidae
- family peronosporaceae
- family pertusariaceae
- family petromyzontidae
- family pezizaceae
- family phaethontidae
- family phalacrocoracidae
- family phalangeridae
- family phalangiidae
- family phalaropidae
- family phallaceae
- family phasianidae
- family phasmatidae
- family phasmidae
- family phillidae
- family phocidae
- family phoenicopteridae
- family phoeniculidae
- family pholadidae
- family pholidae
- family pholididae
- family phthiriidae
- family phyllidae
- family phyllocladaceae
- family phyllostomatidae
- family phyllostomidae
- family phylloxeridae
- family physeteridae
- family physidae
- family phytolaccaceae
- family picidae
- family pieridae
- family pinaceae
- family pinnotheridae
- family piperaceae
- family pipidae
- family pipridae
- family pittidae
- family planning
- family plantaginaceae
- family plasmodiidae
- family plasmodiophoraceae
- family plataleidae
- family platanaceae
- family platanistidae
- family platycephalidae
- family plethodontidae
- family pleurobrachiidae
- family pleuronectidae
- family ploceidae
- family plumbaginaceae
- family pluteaceae
- family poaceae
- family podargidae
- family podicipedidae
- family podocarpaceae
- family poeciliidae
- family polemoniaceae
- family polyangiaceae
- family polygalaceae
- family polygonaceae
- family polynemidae
- family polyodontidae
- family polypedatidae
- family polypodiaceae
- family polyporaceae
- family pomacentridae
- family pomatomidae
- family pongidae
- family pontederiaceae
- family porcellionidae
- family portulacaceae
- family portunidae
- family potamogalidae
- family potamogetonaceae
- family practice
- family priacanthidae
- family primulaceae
- family pristidae
- family procaviidae
- family procellariidae
- family procyonidae
- family proteaceae
- family proteidae
- family prunellidae
- family pseudococcidae
- family pseudomonodaceae
- family psilophytaceae
- family psilotaceae
- family psittacidae
- family psocidae
- family psophiidae
- family psychodidae
- family psyllidae
- family pteridaceae
- family pteriidae
- family pteroclididae
- family pterodactylidae
- family ptilonorhynchidae
- family pucciniaceae
- family pulicidae
- family punicaceae
- family pygopodidae