What is the largest veins in human body?

The largest vein in the human body is the superior vena cava. It is responsible for carrying deoxygenated blood from the upper body to the heart. The superior vena cava is formed by the union of the right and left brachiocephalic veins, which drain blood from the head, neck, and arms. The superior vena cava then descends into the heart and empties into the right atrium.