Daniel Gerhard Brown (born June 22, 1964) is an American writer best known for his thriller novels, particularly the Robert Langdon series Angels & Demons (2000), The Da Vinci Code (2003), The Lost Symbol (2009), Inferno (2013), Origin (2017) and The Secret of Secrets (2025). His novels are treasure hunts that usually take place over a 24-hour period and center on recurring themes of cryptography, art, and conspiracy theories. Brown's books have been translated into 57 languages and have sold over 200 million copies as of 2012. Three of his works—Angels & Demons, The Da Vinci Code, and Inferno—have been adapted into films, while one, The Lost Symbol, was adapted into a 2021 television series. The Robert Langdon novels are deeply engaged with Christian themes and historical fiction, and have subsequently generated controversy. Brown states on his website that his books are not anti-Christian and that he is on a "constant spiritual journey" himself. He states that his book The Da Vinci Code is "an entertaining story that promotes spiritual discussion and debate" and suggests that the book may be used "as a positive catalyst for introspection and exploration of our faith."