Abstract: In the present paper, an orbitoidal foraminifera Ilgazina unilateralis n. gen. n. sp. from the Maastrichtian of Ilgaz-Tosya (S Kastamonu) region has been described and its structural differences have been compared with the taxa showing similar structure. Thenew genus, which very closely resembles the genera Orbitoides, Sivasella and Hellenocyclina, is clearly differentiated from them bythe unilaterally situated chambers on its shell.