Harry Gordon Frankfurt was an American philosopher. He was a professor emeritus of philosophy at Princeton University, where he taught from 1990 until 2002. Frankfurt also taught at Yale University, Rockefeller University, and Ohio State University.

On Bullshit is a 2005 book by American philosopher Harry G. Frankfurt which presents a theory of bullshit that defines the concept and analyzes the applications of bullshit in the context of communication. Frankfurt determines that bullshit is speech intended to persuade without regard for truth. The liar cares about the truth and attempts to hide it; the bullshitter doesn't care if what they say is true or false. Frankfurt's philosophical analysis of bullshit has been analyzed, criticized and adopted by academics since its publication.