- Idotea balthica
- Idotea chelipes
- Idotea emarginata
- Idotea granulosa
- Idotea linearis
- Idotea metallica
- Idotea neglecta
- Idotea pelagica
- Ihlea punctata
- Illex coindetti
- Iphinoe serrata
- Iphinoe trispinosa
- Janthina exigua
- Janthina janthina
- Krohnitta subtilis
- Lamprops fasciata
- Lanice conchilega
- Laodicea undulata
- Lebbeus polaris
- Lensia conoidea
- Lensia fowleri
- Lensia hotspur
- Lepas anatifera
- Lepas anserifera
- Lepas fascicularis
- Lepas hilli
- Lepas pectinata
- Leptomysis gracilis
- Leptomysis lingvura
- Leptomysis mediterranea
- Leptostylis ampullacea
- Leptostylis longimana
- Leptostylis villosa
- Leuckartiara breviconis
- Leuckartiara nobilis
- Leuckartiara octona
- Leucon acutirostris
- Leucon fulvus
- Leucon nasica
- Leucon nasicoides
- Leucon pallidus
- Limacina lesueuri
- Limacina retroversa
- Limacina retroversa balea
- Limacina retroversa retroversa
- Liriope tetraphylla
- Lizzia blondina
- Loligo forbesii
- Loligo vulgaris
- Lophogaster typicus