This study presents a novel vibration energy harvesting strategy that integrates a nonlinear X-shaped structural configuration with piezoelectric elements, utilizing both horizontal and vertical mounting orientations to exploit structural coupling and nonlinear dynamics. Departing from conventional approaches that primarily focus on the intrinsic nonlinearity of beam-based harvesters, this research investigates the additional benefits introduced by the X-shaped geometry. The proposed system combines the advantages of traditional cantilevered beam harvesters, which operate near the beam’s natural frequency, with those of spring-mass supported configurations, typically constrained to the spring-mass system’s resonance. The incorporation of X-structures significantly extends the operational bandwidth, enabling effective energy harvesting in the ultralow frequency domain. This enhanced tunability allows for precise adjustment of the initial resonant peak through manipulation of structural parameters, distinguishing the design from standard cantilevered and spring-mass systems. The findings offer a new framework for developing nonlinear piezoelectric energy harvesters with improved efficiency across a broad frequency range, from ultralow frequencies to the beam’s natural resonance.