Tenellia is a genus of sea slugs, aeolid nudibranchs, marine gastropod molluscs in the family Trinchesiidae.

[3] Miller (2004) restricted the genus Cuthona Alder & Hancock, 1855 to the type species, C. nana (Alder & Hancock, 1842), and transferred to the genus Trinchesia the rest of the species previously included in Cuthona.

Miller has been followed by some authors, and has not been followed by others - and there is currently much instability on the extension and contents of these two genera.

Cella et al., 2016 hypothesised that the genus Tenellia should include many former Cuthona and Trinchesia species, with others being placed in new genera.

Until the species listed here are re-investigated they are left by WoRMS in the genus Trinchesia.