Robert Langdon is a fictional character, Professor of Religious Symbology at Harvard University, in the novels Angels and Demons and The Da Vinci Code by Dan Brown. He is also a well-respected scholar.

At the beginning of "Angels and Demons", Robert Langdon is called to CERN headquarters in Switzerland to find out the religous symbological relationship to the murder of a scientist. When he arrives he starts a journey to the Vatican to find he ancient lair of an evil anti-religous organization deeply ingrained into most institutions, the Illuminati. Robert Langdon solves many codes and mysteries to track down the heinous murderer of the scientist, along with the reason why everything happened. At the beginning of The Da Vinci Code, he is in Paris to give a lecture on his work. Having made an appointment to meet with Jacques Saunière, the curator of the Louvre, he is startled to find the French police at his hotel room door. They inform him that Saunière has been murdered and they would like his immediate assistance at the Louvre to help them solve the crime. Unbeknownst to Langdon, he is in fact the prime suspect in the murder and has been summoned to scene of the crime in order that the police may extract a confession from him. He spends the rest of the novel dodging the police and trying to solve the mystery left for him by Saunière.