Agathotoma merlini is a species of sea snail, a marine gastropod mollusk in the family Mangeliidae.

[1] First described in 1910, its species name refers to Martial Henri Merlin, governor-general of French Congo.

The shell's sculpture includes longitudinal ribs, which are narrower than their intervals, numbering 10 on the body whorl, with extremely fine striae visible only under magnification.

The last three whorls exhibit a brown subsutural zone, interrupted by the lower extremities of the ribs, which remain white.

[2] It occurs on the westcoast of Africa (Mauritania and Senegal), and also on the islands of São Tomé and Príncipe.