Occidenthella is a genus of sea slugs, specifically aeolid nudibranchs, in the family Flabellinidae.

[4] The only described species is Occidenthella athadona, a combination named in 2017.

[a] It was originally described as Coryphella athadona in 1875.

[2] The genus name Occidenthella, from occidens, meaning "west" in Latin, refers to its distribution in the Western Pacific Ocean.

[1][3][5] In the 2017 publication, it was placed in the reinstated family Coryphellidae.