Edmund L. Gettier III (born 1927, Baltimore, Maryland) is an American philosopher best known for the so-called Gettier problem in epistemology which he outlined in a 1963 paper in Analysis titled "Is Justified True Belief Knowledge?". Gettier is Professor Emeritus at the University of Massachusetts at Amherst.
The Gettier problem is a response to the standard account of knowledge as being justified true belief. This account originated in Plato's Theaetetus and the Meno; Gettier cited Roderick Chisholm's version of justified true belief in Perceiving: A Philosophical Study and A. J. Ayer's account from The Problem of Knowledge. Gettier's paper describes a class of counter-examples to the justified true belief account, where one has a justified belief that p is true, and p happens to be true, but the justification for p doesn't bear any relationship to the truth of the matter. For instance, if you saw a man driving a blue car down the street, you might infer that he owns a blue car. It turns out that the car he is driving is stolen or borrowed, but at home the man does in fact have a blue car. The belief is true, but the justification for it points to the wrong thing being true.