A small bump on the medial border of the ischial body anterior to the acetabular notch. To this bump attaches the superior ligamentous band of the obturator membrane. Above this band is the obturator sulcus.

Obturator derives from the Latin verb obturare denoting to occlude or cover over. The foramen is so named because it is covered over by muscles and a ligamentous membrane. Tubercle comes from the Latin tuber meaning a lump, combined with the diminutive ending denoting a small lump.