Specimens of Sinum haliotoideum (Linnaeus, 1758) were recently collected in the Red Sea area, confirming an old report from the mid-1800s. The occurrence in the Red Sea is supported by records, both earlier and recent, from neighbouring localities in the northern Indian Ocean. Thus, the northern Indian Ocean, including the Red Sea, has to be included in the geographical range of this spe­cies. Differences in opinion concerning conspecificity of Sinum haliotoideum with other species of Sinum described from the Indo-Pacific are discussed. S. planulatum (Récluz in Chenu, 1843) = S. planatum (Récluz in Chenu, 1843), S. planum (Philippi, 1844), S. gualterianum (Récluz, 1851), and S. weberi (Bartsch, 1918) are all junior synonyms of S. hali­otoideum (Linnaeus, 1758). S. fuscum (Röding, 1798), S. sin­uatum (Récluz, 1851), S. lacteum (Récluz, 1851), Ectosinum pauloconvexum Iredale, 1931, and S. diauges Kilburn, 1974 are distinct from S. haliotoideum. The status of S. indicum (Gray, 1828) remains uncertain as the type material is prob­ably lost.