Lightweight aggregate concrete (LWAC) has received a lot of attention in the construction sector due to its distinct qualities and benefits. Moreover, the addition of fiber to the LWAC mix can enhance its mechanical properties, and the use of fiber-reinforced LWAC is increasing in the construction sector. This type of concrete is used in bridges, floor slabs in high-rise buildings, off-shore structures, highways, pavements and airport runways. In these types of structures, flexural stress is critical, so it is important to investigate the fatigue effect on this type of concrete structures that use this LWAC at various stress levels. When compared to normal concrete, lightweight aggregate concrete can significantly reduce self-weight in engineering structures. As per limited information in the literature, the fatigue performance of LWAC is not the same as normal-weight concrete. Therefore, it is important to conduct more studies on the fatigue performance of LWAC. This thesis investigates the flexural fatigue strength and fatigue life distribution of plain and fiber-reinforced lightweight aggregate concrete (LWAC) under various stress levels. The flexural fatigue test data for plain and fiber reinforced LWC is collected from literature. The fatigue performance of different types of LWAC was evaluated using conventional Wöhler fatigue equation and power relations (double logarithmic fatigue equations). The effect of different types of fibers (hook-ended fiber, twisted fiber, polypropylene fiber and mix fibers) on the fatigue performance was also evaluated. Probabilistic fatigue analysis was conducted on the collected fatigue test data to evaluate the fatigue performance for different failure probabilities. The analysis used two parameter Weibull distribution (2PWD) and three-parameter Weibull distribution (3PWD) models. There are limited experimental studies conducted in this field for the LWAC. Therefore, the analyzed data were collected from two different studies. The results show that fiber reinforcing can significantly increase the fatigue resistance of LWAC. Both plain and fiber-reinforced LWAC's fatigue life follows the Weibull distribution, with shape and scale parameters that depend on the applied stress amplitude. By taking into account failure probability, the double and single logarithmic fatigue equations were developed to establish the fatigue life equation. It was found that the 3PWD represents the fatigue failure more accurately than the 2PWD because of its nonlinear curve, which is the real case of fatigue failure. Moreover, the results of stress level for two million cycles (N=2106 ) obtained using 3PWD were better than those obtained by 2PWD.