15 valid species and 3 doubtful species Tethydidae is a family of dendronotid nudibranch gastropod molluscs in the superfamily Dendronotoidea.

[3] The original spelling (subfamily) is Tethydia.

It was placed on the Official List by Opinion 1182 of ICZN (1981: 174), which also ruled that the name should be corrected to Tethydidae (Bouchet & Rocroi, 2005).

This family is within the clade Cladobranchia and has no subfamilies (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005).

[2] There are two[1] genera within the family Tethydidae: Species in this family do not possess a radula.