"Naruto's Birth" (ナルトの出生, Naruto no Shusshō, Viz: The Birth of Naruto) is chapter 500 of the original Naruto manga.
Kushina tells Naruto the history of her clan, and how she became the second Nine-Tails' jinchūriki. After that she begins to explain the events that took place on the day of his birth sixteen years ago. She mentions that the birth took place in secret, as the seal that was keeping the Nine-Tails could possibly break. Soon after Naruto's birth, a masked man killed all the Anbu guarding the cave where he was born. He took Naruto hostage, and told the Fourth Hokage to step away from the jinchūriki, or he would kill the new born.