The present thesis examines the varied phenomena of tiredness, neither from a psychological, nor a sociological point of view, but focuses on analysing this particular condition from a philosophical mainly phenomenological viewpoint. Since tiredness is a physical phenomenon as well as that of a living body, these two levels are examined and differentiated as far as possible in the beginning. Following this introduction, the neuroscientifically detectable symptoms of fatigue are identified. The main part of this thesis treats tiredness using the method of living body phenomenology. The change of consciousness and the sense of time of the tired person show themselves as particularly significant for this. In conclusion a definition of this complex phenomenon is given.