Middle Permian (Midian in the Tethyan standard scale) foraminifers of 34 species assignable to 27 genera were identified in erratic limestone blocks collected on the left bank of the middle course of the Kuma River (Osakama), west Kyushu, Japan, where four species of fusulinoideans have been reported. These blocks are thought to have been derived from a small limestone contained in basaltic rocks embedded within uppermost Jurassic mudstone along the southern margin of the Chichibu Terrane (Sambosan Terrane). An Osakama foraminiferal fauna in comparison with contemporaneous faunas known from the Jurassic to Early Cretaceous terranes of Japan and in relation to the limestone lithology are described and discussed in this paper. The Osakama fauna is characterized by dominant occurrence of a newly proposed species Yabeina osakamensis contained in weakly dolomitized gray limestone consisting of fusulinoidean crinoidal bioclastic packstone/grainstone with lithic clasts of limestone. The limestone lithology and bioclasts of a primitive species of Pseudodoliolina suggest that limestone deposition initiated on the Sambosan Seamount in equatorial Panthalassa as early as early Middle Permian (early Murgabian in the Tethyan scale). The Osakama fauna is more closely related to the Kaize fauna than the Gozenyama, both of which are known from the Southern Chichibu Terrane of the Kanto Mountains. Yabeina globosa, a diagnostic species in the fusulinoidean faunas of the Chichibu and Tamba-Mino-Ashio terranes and common in black to dark gray micritic limestone, is completely absent in the present Osakama and Kaize faunas.