Naruto's father's name is Minato Namikaze, and mother is Kushina Uzumaki. So, why is Naruto's surname Uzumaki? Shoudn't it be Namikaze?
In Naruto "Ch.440: A Conversation with the 4th" it is stated that the third Hokage wanted as little information about the Kyuubi out in public as possible and that's why nobody, not even Naruto should know that Minato was his father. Thus he was given the name Uzumaki instead of Namikaze.
Page 5: "If anyone knew you were my son, you'd have been in constant danger"