What is the name of the main character of many Dan Brown's novels?

Daniel Gerhard Brown (born June 22, 1964) is an American author best known for his thriller novels, including the Robert Langdon novels. His novels are treasure hunts that usually take place over a period of 24 hours. They feature recurring themes of cryptography, art, and conspiracy theories. His books have been translated into 57 languages and, as of 2012, have sold over 200 million copies. Three of them, Angels & Demons, The Da Vinci Code, and Inferno, have been adapted into films.

Professor Robert Langdon is a fictional character created by author Dan Brown for his Robert Langdon book series: Angels & Demons (2000), The Da Vinci Code (2003), The Lost Symbol (2009), Inferno (2013) and Origin (2017). He is a Harvard University professor of history of art and "symbology" (a fictional field related to the study of historic symbols, which is not methodologically connected to the actual discipline of semiotics).

Tom Hanks portrays Langdon in the Robert Langdon film series, starting with the 2006 film adaptation of The Da Vinci Code, reprising the role in the 2009 film adaptation of Angels & Demons, and again in the 2016 film adaptation of Inferno.