Alphaabyssovirus is a genus of positive-strand RNA viruses in the order Nidovirales which infect sea hares.

[2] The genus is monotypic.

It contains only the subgenus Aplyccavirus, which contains only one species, Aplysia abyssovirus 1.

[1] Alphaabyssovirus is also the only member of the subfamily Tiamatvirinae, which in turn is the only member of family Abyssoviridae, which likewise is the only member of the Abnidovirineae suborder.

[1] Aplysia abyssovirus 1 was first isolated from a sample from a California sea hare (Aplysia californica).