Constitution states any candidate for presidency must be natural born American citizen, meaning can't have immigrated and then attained citizenship. I believe his father is Kenyan by birth, but I could be wrong
RaulDiaz007 is right. But, I'd just like to point out some facts for people who don't understand how citizenship works...
"You may become a U.S. citizen either at birth or after birth. Individuals who are born in the United States and subject to the jurisdiction of the United States and individuals born in certain territories or outlying possessions of the United States are citizens at birth. Also, individuals born outside the United States may be citizens at birth if their parent or parents were citizens at the time of birth and other requirements are met."
Yes! He was born in the UNITED STATES OF AMERICA. His father was in the U.S. in college as an exchange student and that's how he met Obama's mother. I'm not sure why so many people think Obama was born in another country???