The leader of the Nazi Party who wrote "Mein Kampf" was Adolf Hitler. This autobiographical manifesto, published in 1925, outlined Hitler's political ideology, including his ideas on race, anti-Semitism, nationalism, and the desire for German expansion. "Mein Kampf" became a foundational text for Nazi philosophy, laying the groundwork for the party's policies and the eventual implementation of oppressive and violent practices during Hitler's regime. The book reflects Hitler's worldview and ambitions, playing a significant role in spreading Nazi propaganda, influencing public opinion, and justifying the atrocities committed during the Holocaust.