Candice Sue Millard is an American writer and journalist. She is a former writer and editor for National Geographic and the author of The River of Doubt: Theodore Roosevelt's Darkest Journey, a history of the Roosevelt–Rondon Scientific Expedition, Theodore Roosevelt's exploration of the Amazon Rainforest in 1913 and 1914. The River of Doubt, published in 2005 by Doubleday, was a New York Times Best Seller. Millard's second book, Destiny of the Republic: A Tale of Madness, Medicine & the Murder of a President, was released in September 2011, and is also a New York Times Best Seller.