The common iliac vein (latin: vena iliaca communis) is a large vein in the human body formed by the external iliac and internal iliac veins.
The common iliac vein begins anterior to the sacroiliac joint, where the internal iliac vein joins the external iliac vein. The common iliac vein passes obliquely upward to the fifth lumbar vertebra, a little to its right. At this point both common iliac veins come together and form the inferior vena cava.
On its way the common iliac vein collects the iliolumbar and sometimes the lateral sacral veins.
The common iliac veins drain blood from the pelvis and the lower limbs.