Harsha was the grandson of a Gupta Princess. At 16, he became the king, when his brother Rajyavardhana was killed. Harsha ruled from Thaneswar. He consolidated his kingdom, with the help of his widowed sister, the queen of Kannauj.

Harshavardhana's reign is well-documented by his court poet, Bana-Bhatta. The Chinese buddhist pilgrim, Hieun Tsang, also documented Harshavardhana's reign in his travels accounts.

The area under Harshavardhana's control covered Punjab, eastern Rajasthan and the Ganga valley as far as Assam. He governed his empire on the same lines a the Guptas. The kings he conquered paid him revenue and sent soldiers when he was fighting war. They accepted his sovereignty, but remained rulers over their own kingdoms. Harshavardhana's ambition of extending his power to the Deccan and southern India were stopped by Chalukya king Pulakesin II.

Harsha died without any heirs, and his kingdom disintegrated rapidly into small states. After the downfall of Harshwardhan's empire, two empires rose to prominence: Pala in the East, and Pratihars in the West.