Plakobranchidae is a family of sea slugs, marine opisthobranch gastropod mollusks in the superfamily Plakobranchoidea.

[2] They superficially resemble nudibranchs but they are sacoglossans, members of the clade Sacoglossa within the Opisthobranchia.

Elysiidae was originally described as "Elysiadae" by Forbes & Hanley in 1851 in the book A history of British Mollusca and their Shells 3:613.

Franc (1968: 848) and Jensen (1996: 92) attributed the name to Rang, 1829 (p. 134), who used the vernacular "les Placobranches".

Bouchet & Rocroi (2005: 133), argued that the spellings Placobranchus and Placobranchidae were in prevailing usage and were conserved under Art.