Authenticity is a widespread but ambiguous notion in our collective imagination. Cut off from its essentialist roots by various schools of twentieth-century philosophy, it has come to be shaped, as a discursive construct, by popular culture rather than scholarly thought. This article examines selected works of Ernest Hemingway, who became one of the most influential creators and arbiters of authenticity in modern (popular) literature but who constantly subjected the concept to critical scrutiny in his fiction. This ambivalent attitude grew out of Hemingway's interaction with the modernist literary field. Initially, posturing as an authentic writer served to distinguish him from the urban bohème. Later, as the posture became fashionable and threatened to lose its distinctive function, he questioned and refined it on a regular basis in his works, which thus allows us a glimpse at the collective imagination of authenticity in the making.