A new approach for the definition of the critical plane and a new energy-based multiaxial fatigue parameter are proposed in this work. The normal strain energy and shear strain energy on two orthogonal material planes are used to predict fatigue damage in multiaxial fatigue loading. The influence of the Poisson effect, mean normal strain energy and the different contribution of the compressive and tensile normal strain energies are accounted for. An energy-based parameter is defined which explains the different effects of the total strain energy on different material directions. Experimental data are used to validate the capabilities of this new multiaxial fatigue parameter, including 10 materials and 33 loading paths, which cover most of the commonly used loading conditions in multiaxial fatigue tests. The results show that the proposed multiaxial fatigue parameter gives good predictions (within a life factor of two) for most of these materials and loading paths. (C) 2017 Elsevier Ltd. All rights reserved.