Limacia janssi is a sea slug, a species of dorid nudibranch.

It is a marine gastropod mollusc in the family Polyceridae.

[2] Limacia janssi was described from Bahia Santa Elena, 10°56′N 85°49′W / 10.933°N 85.817°W / 10.933; -85.817, Guanacaste, Costa Rica.

Additional specimens from Isla Partida, 24°33′N 110°24′W / 24.550°N 110.400°W / 24.550; -110.400, Gulf of California, Mexico were included in the original description.

It has also been reported from Isla San Pedro Mártir, Gulf of California.