Multiferroic altermagnets, which integrate ferroelectricity with altermagnetism, provide a promising platform for realizing unconventional magnetoelectric coupling. However, the realization of multiple multiferroic orders in such systems remains largely unexplored. Here, we uncover electrically reconfigurable altermagnetism in three-dimensional (3D) van der Waals (vdW) crystals assembled from orthogonally stacked ferromagnetic (FM) transition metal oxytrihalide nanowires. Taking ${\mathrm{MoOBr}}_3$ as an example, first-principles calculations identify a ferroelectric (FE) ground state and four metastable polar variants—ferrielectric (FiE) plus three symmetry-inequivalent antiferroelectric (AFE) configurations—created by Mo off-center movement along the nanowire axis. All five phases retain altermagnetic (AM)-like nonrelativistic spin splitting characteristics, while spinorbit coupling (SOC) merely endows each with a distinct magnetic-anisotropy landscape. Crucially, controlled switching among the FE, AFE, and FiE states concurrently reshapes the momentum-resolved spin splitting and rotates the Néel vector by up to ${90}^{\circ }$, revealing a strong coupling between electric polarization and AM order. Additionally, uniaxial strain breaks the $C_{4x}$ symmetry protection, inducing a piezomagnetic response that transforms the compensated AM state into a weakly ferrimagnetic (FiM) state while simultaneously modulating the FE polarization magnitude. This synergy and coupling of multiple multiferroic orders hold potential candidates for developing nonvolatile memories, reconfigurable logic devices, and energy-efficient mechanospintronics.

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• Electronic structure
• Ferroelectricity
• Magnetic order
• Spin-orbit coupling
• Multiferroics
• First-principles calculations