Sahadeva (Sanskrit: सहदेव) is the youngest of the five Pandava brothers in the ancient Indian epic, the Mahabharata. He and his elder twin Nakula are described as the sons of Madri, one of the wives of the Pandava patriarch Pandu, and the Ashvins, the divine twin physicians of the gods, whom she invoked to beget sons owing to Pandu's inability to procreate. Within the tradition, Sahadeva is renowned for his wisdom, his knowledge of astrology, and his skill in swordsmanship.
Like his brothers, Sahadeva was married to Draupadi. He also married Vijaya, a princess of the Madra kingdom. He had two sons, Shrutasena from Draupadi and Suhotra from Vijaya. During the Rajasuya sacrifice of his eldest brother Yudhishthira, Sahadeva is said to have led the conquest of the kings of the South.
After Yudhishthira lost all his possessions to Duryodhana in the game of dice, Sahadeva vowed to slay Shakuni, Duryodhana's maternal uncle, who had employed loaded dice to win unfairly. The Pandavas and Draupadi were thereafter exiled for thirteen years, the final year being a period of concealment known as Agyaata Vaasa. During this period, Sahadeva took up the disguise of a Vaishya named Tantripala and served as a cowherd in the kingdom of Virata.
In the Kurukshetra War between the Pandavas and the Kauravas, Sahadeva fought as a skilled warrior, and on the eighteenth day of the war he slew Shakuni, fulfilling his earlier vow. At the close of the epic, during the Pandavas' final journey through the Himalayas towards Svarga, Sahadeva is described as the second to fall after Draupadi, on account of excessive pride in his own wisdom.
Adapted from the English Wikipedia article on Sahadeva.