A comprehensive worldwide list of 425 species of the ladybird genus Diomus Mulsant, 1850, is provided, together with the number of countries occupied by each species in the major biogeographical regions. Thirteen of the species formally assigned to the genus must be confirmed. Also, records of Diomus species occurring in the Middle East are documented, and the genus Diomus is reported from Oman for the first time, based on a female specimen of an undetermined species. Findings exclude previous r