No, he is Christian, baptized in the United Church of Christ in 1988.
The idea that he is Muslim stems from his childhood in Indonesia. In the one year he spent at a public school, the school administration registered him as a Muslim, but only (probably) because his stepfather was (although friends and family recall him of being more of a “free spirit” than affiliated with any single religion – in one of his books, Obama wrote that his stepfather, “followed the same kind of Islam as many Indonesians, ‘a brand of Islam that could make room for the remnants of more ancient animist and Hindu faiths’”.
Though the school in Jakarta was public, as Indonesia is predominantly Muslim, there were weekly religious classes (following “government curriculum”) during which Obama learned about Islam. Moreover, Obama attended a Catholic school for three years while in Indonesia. Those who knew him back then say Obama only accompanied his stepfather to mosque, which was a very rare occurrence, because his stepfather was usually too busy to go. Obama was even baptized in 1988, and was married in a Christian Church.