- Pachynemertes
- Pachynemertes
- Pachynemertidae
- Pachynemertidae
- Palaeonemertea
- Panorhynchidae
- Panorhynchidae
- Panorhynchus
- Panorhynchus de la Serna de Esteban & Moretto, 1969
- Parabalaenanemertes
- Parabalaenanemertes Brinkmann, 1917
- Paracerebratulus
- Paracerebratulus Senz, 1997
- Paradinonemertes
- Paradinonemertes Brinkmann, 1915
- Paradrepanophoridae
- Paradrepanophoridae
- Paradrepanophorus
- Paradrepanophorus Stiasny-Wijnhoff, 1926
- Parahubrechtia
- Parahubrechtia Gibson & Sundberg, 1999
- Paralineopsis
- Paralineopsis Iwata, 1993
- Paralineus
- Paralineus Schütz, 1911
- Paramicrura
- Paramicrura Gibson & Sundberg, 1992
- Paramicrurinella
- Paramicrurinella Gibson, 1985
- Paraminutanemertes
- Paraminutanemertes Senz, 1993
- Paranemertes
- Paranemertes Coe, 1901
- Paranemertopsis
- Paranemertopsis Gibson, 1990
- Parapolia
- Parapolia Coe, 1895
- Parborlasia
- Parborlasia Friedrich, 1970
- Parischyronemertes
- Parischyronemertes Gibson, 2002
- Paroerstedia
- Parvicirrus
- Parvicirrus Ris, 1993
- Peavinenemertes Iwata, 2011
- Pelagica
- Pelagonemertes
- Pelagonemertes Moseley, 1875
- Pelagonemertidae
- Pelagonemertidae
- Pendonemertes
- Pendonemertes Brinkmann, 1917
- Perissonemertes
- Perissonemertes Gibson, 1990
- Phallonemertes
- Phallonemertes Brinkmann, 1917
- Phallonemertidae
- Phallonemertidae
- Pheroneonemertes
- Pheroneonemertes Gibson, 1990
- Phylline
- Planaria
- Planaria
- Planktonemertes
- Planktonemertes Woodworth, 1899
- Planktonemertidae
- Planktonemertidae
- Planonemertes
- Planonemertes Coe, 1926
- Plectonemertes
- Plectonemertes Gibson, 1990
- Plectonemertidae
- Plectonemertidae
- Plenanemertes
- Plenanemertes Coe, 1954
- Plionemertes
- Plionemertes Coe, 1926
- Plotonemertes
- Plotonemertes Brinkmann, 1917
- Poikilonemertes
- Poikilonemertes Stiasny-Wijnhoff, 1942
- Polia
- Polina Stimpson, 1857
- Poliopsis
- Poliopsis Joubin, 1890
- Polybrachiorhynchidae
- Polybrachiorhynchidae
- Polybrachiorhynchus
- Polybrachiorhynchus Gibson, 1977
- Polyschista
- Polyschista Wijnhoff, 1925
- Polystemma
- Polystemma
- Polystilifera
- Polystilifera
- Pontolineus
- Pontolineus
- Poseidon
- Poseidon
- Poseidonemertes
- Poseidonemertes Kirsteuer, 1967
- Potamostoma Kajihara, Gibson & Mawatari, 2003
- Praealbonemertes
- Praealbonemertes Cantel, 1993
- Proarmaueria
- Proarmaueria Coe, 1926
- Proarmaueriella
- Proarmaueriella Tshernyshev in Chernyshev, 1992
- Probalaenanemertes
- Probalaenanemertes
- Procarinina Bergendal, 1902
- Proneurotes
- Proneurotes Montgomery, 1897
- Prosadenoporus
- Prosadenoporus Bürger, 1890
- Prosorchochmus
- Prosorhochmidae
- Prosorhochmidae
- Prosorhochmus
- Prosorhochmus Keferstein, 1862
- Prostoma
- Prostoma Duges, 1828
- Prostomatella
- Prostomatella Friedrich, 1935
- Prostomiopsis
- Prostomiopsis Friedrich, 1936
- Protetrastemma
- Protetrastemma Chernyshev, 2004
- Protopelagonemertes
- Protopelagonemertes Brinkmann, 1917
- Protopelagonemertidae
- Protopelagonemertidae
- Protubulanus
- Protubulanus Chernyshev, 1995
- Pseudobaseodiscus
- Pseudobaseodiscus Senz, 1993
- Pseudocarcinonemertes
- Pseudocarcinonemertes Fleming & Gibson, 1981
- Pseudomicrura Strand & Sundberg, 2011
- Ptychodes
- Punnettia
- Punnettia Stiasny-Wijnhoff, 1926
- Pussylineus
- Pussylineus Corrêa, 1956