The author of the famous diary that documented life during the Holocaust is Anne Frank. Her diary, "The Diary of a Young Girl," chronicles her life in hiding from the Nazis in Amsterdam. It provides poignant insights into her thoughts, fears, and aspirations during this harrowing time. Frank’s powerful narrative highlights the human experience amidst atrocity, and her story continues to resonate as a symbol of resilience and the enduring fight against oppression.