A new entomopathogen, Hirsutella cryptosclerotium, is described from the mealybug pest, Rastrococcus invadens, collected in Togo, West Africa. The fungus forms dark, subglobose to irregular pseudoparenchymatous sclerotia within the host and in both solid and liquid culture. The production of internal sclerotia distinguishes this taxon from the closely related H. thompsonii and H. sphaerospora. The differentiated gelatinous conidial sheath, characteristic of this species complex, is illustrated using both SEM and TEM techniques. The pathogenicity, life-cycle and biocontrol potential of H. cryptosclerotium are briefly discussed.