Half the Sky: Turning Oppression into Opportunity for Women Worldwide is a nonfiction book by husband and wife team Nicholas Kristof and Sheryl WuDunn published by Knopf in September 2009. The book argues that the oppression of women worldwide is "the paramount moral challenge" of the present era, much as the fight against slavery was in the past. The title comes from the 1968 statement by Mao Zedong "妇女能顶半边天", meaning "women hold up half the sky", though the authors cite it only as a "Chinese proverb".