Vajji was a mahajanapada towards the north of Ganga in the division of Tirhut. It was a confederacy of eight or nine clans. The capital of Vajji mahajanapada was situated at Vaishali.
According to the Chera poets, Senguttuvan was their greatest king. He is also known as the Red or Good Chera. He led many successful military expeditions. He has also been mentioned in the post-Sangam text, Silappadikaram.