Natural animals such as crotaline and boid snakes have the ability to detect infrared radiation, which is emitted by any living object while it is invisible to human eyes. To evade thermal detection, various attempts, such as the stealth or low observability technologies, are generally made to reduce the infrared signature. However, the validity of these technologies is background dependent. In this paper, the first, large‐scale, far‐infrared, unidirectional invisibility cloak in air environment is experimentally demonstrated. The cloak constructed from germanium can smoothly guide the infrared wave around the hidden object when facing the incident wave direction. The cloak works for full polarization in a broad far‐infrared spectrum. This work provides a new way to manipulate infrared radiation for future applications.