Stretchable sensors capable of detecting various mechanical stimuli are essential in wearable applications involving multiaxial motions. Previous wearable sensors are designed for sensing only single-axis deformation or multidimensional strains in a two-dimensional plane. Given the three-dimensional (3D) nature of multiaxial stimuli in practical applications, discriminating multidimensional strains in 3D space is critical and requires an integration of different anisotropic sensors for high sensitivity and selectivity. In this study, a skin-inspired multidimensional sensor capable of sensing 3D stimuli is developed by rationally integrating three sub-sensors, which simultaneously and selectively measure strains in three orthogonal axes. The 3D anisotropic sensing characteristics of the sub-sensors arising from their highly anisotropic structures enable the differentiation of 3D stimuli including in-plane tension, normal pressure and shear, and the distinction of in-plane strain directions with an unprecedented selectivity of 3.68 among existing stretchable sensors. With a remarkable gauge factor of 168 for in-plane strains and high sensitivity of 0.62 kPa(-1)for normal pressure, the sensor is used in a smart sport assistant that can evaluate sport performance and provide feedback in real-time. The findings in this work provide a new anisotropic design of multidimensional sensors for emerging applications, such as smart electronics and humanoid robots.