Alvania ignota is a species of minute sea snail, a marine gastropod mollusk or micromollusk in the family Rissoidae.
The length of the shell is of small size (holotype 2,2 x 1,2 mm), the shell is conic-ovate, thick, has beaded spiral cords and convex whorls. It is imperforate, vitreous, and colourless.
Protoconch: 1,5 whorls (at 40X smooth).
Teleoconch: three convex whorls, suture impressed and wide. In the last whorl there are 7 spiral cords (3 of which are in the second whorl) with strongly circular beads when they are crossed by about 20 weaker axial ribs. The distance between 2ð and 3ð cord is larger. The mouth of the snail is oval in shape, with the outer lips having a strong varix. The snail has no umbilicus, while the Operculum and soft parts are unknown.
This species occurs in the Indian Ocean off Southern Madagascar; Réunion; Mauritius.