An overview of multiaxial fatigue life prediction methodologies and tests is provided in the present paper. It is essential for engineering applications to accurately estimate the fatigue failure behaviour and fatigue life of structures or materials subjected to multiaxial loads. Several multiaxial fatigue criteria and metal materials are reviewed in this research, including materials such as steel S355, titanium alloy TC4, 42CrMo4, AISI 303, SM45C, SAE1045, and LY12CZ. It is noted that if the fatigue life prediction models created under multiaxial constant amplitude loading were applied to the life prediction of the complicated multiaxial load, right techniques for the critical plane determination and multiaxial fatigue damage parameter setting would be required. Multiaxial stress experiments are much more complicated and costly than uniaxial fatigue experiments. Unfortunately, neither the damage produced by a multiaxial fatigue stress state nor the method for assessing it are well recognized. Consequently, it is a fully unexplored subject that continues to be investigated. Existing multiaxial non-proportional fatigue methods are restricted to the theoretical research phase, with limited practical applications. The fundamental reason is that the engineering load is complicated and unpredictable. As mentioned, multiaxial fatigue is a complicated phenomenon; thus, it should not be transformed into an equal condition of uniaxial stress using a simple static premise.