This article offers a general discussion of the concept of false hope. Its ultimate aim is to clarify the meaning and the relevance of that concept for medicine and medical research. In the first part (Sections I-V), the concept of hope is discussed. I argue that hope is more than a combination of a desire and a belief about the probability that the desire will be fulfilled. Imagination and anticipation are as well components of hope. I also discuss if hope implies orientation to action. In the second part (Sections VI-VIII), I examine the concept of false hope. I show that hope is false if it cannot be justified epistemically. There is, I argue, an intimate relation between false hope and ignorance. Hope is justified-"realistic"-when the hoping person knows and accepts experts' judgement about the probability of hope fulfillment. I then argue that what matters for evaluating a person's hope is not only whether it is realistic, but also whether it is reasonable in the light of the aim and goals that a person strives for in (the remainder of) his life. Part three (Sections IX and X) goes into the question of what is morally wrong about having or causing false hope. In the fourth part (Sections XI and XII), the relevance is shown of the insights from the previous parts for the debate on false hope in medicine and clinical research. © 2019 The Author(s).