This book covers several aspects of the fatigue behavior of textile and short fiber reinforced composites. The first part is dedicated to 2D and 3D reinforced textile composites and includes a systematic description of the damage evolution for quasi-static and tensile-tensile fatigue loadings. Acoustic emissions and digital image correlation are considered in order to detect the damage modes’ initiation and development. The acoustic emission thresholds of the quasi-static loading are connected to the “fatigue limit” of the materials with distinctions for glass and carbon reinforcements.<br />The second part is devoted to the fatigue behavior of injection molded short fiber reinforced composites. Experimental evidence highlights the dependence of their fatigue response on various factors: fiber and matrix materials, fiber distribution, environmental and loading conditions are described. A hybrid (experimental/simulations) multi-scale method is presented, which drastically reduces the amount of experimental data necessary for reliable fatigue life predictions.