This lecture introduces the concept of fatigue in materials, explaining how materials respond to repeated stress cycles, leading to potential rupture. Topics covered include the influence of material properties on fatigue resistance, the Wöhler curve, and the endurance limit. The instructor discusses the impact of stress amplitude, mean stress, and the number of cycles on material fatigue behavior, emphasizing the distinction between high-cycle and low-cycle fatigue. Practical examples such as the fatigue failure of a bolt and a tire are used to illustrate these concepts.