Shantanu was a Kuru king of Hastinapura, who is mentioned in the Mahābhārata epic. He was a descendant of the Bharata race, of the lunar dynasty and the ancestor of the Pandavas and the Kauravas. The Rigveda (X.98.11) mentions Shantanu. He was the youngest son of King Pratipa of Hastinapura and had been born in the latter's old age. The eldest son Devapi suffered from leprosy and abdicated his inheritance to become a hermit. The middle son Balhika devoted his life to conquer Balkh. Shantanu become the king of Hastinapura by default.

Read more about Shantanu:  Shantanu and Ganga, Shantanu and Satyavati