Two-dimensional (2D) low-symmetry semiconductors exhibit intrinsic in-plane anisotropy that is attractive for directional nanoelectronic and optoelectronic applications, yet high-performance candidates remain limited. Using density functional theory, we systematically investigate the structural stability and electronic anisotropy of monolayer (1L) and bilayer black arsenene (b-As) with $\mathit{AA}, \mathit{AB}, \mathit{AC}$, and $A\delta$ stacking configurations. Relative energy calculations identify $\mathit{AB}$ stacking as the ground-state bilayer structure, while $\mathit{AA}, \mathit{AC}$, and $A\delta$ are metastable but dynamically stable within the considered configurations. All structures retain semiconducting character, with stacking-dependent band dispersions and band gap magnitudes. Tensile strain along the armchair direction efficiently modulates the band gap, with the $\mathit{AB}$ bilayer exhibiting the strongest response, showing a reduction of up to 0.9 eV at $6\%$ strain, indicative of pronounced anisotropic deformation potentials. A perpendicular electric field (EF; $\pm 0.5\mathrm{V}/\AA$) produces negligible band gap variation in the 1L but induces substantial and continuous band gap tuning in bilayers due to interlayer potential asymmetry, most prominently in the $\mathit{AB}$ stacking, which maintains a robust and continuously tunable band gap across the entire field range. Twist-induced interlayer coupling further alters the electronic anisotropy: A ${90}^{\circ }$ twisted bilayer exhibits nearly isotropic in-plane band dispersion, while external EFs restore anisotropic features by breaking the symmetry between rotated layers. These results demonstrate that stacking order, strain, twist angle, and electrostatic gating provide independent and effective control parameters for engineering the magnitude and directional character of the band structure in b-As, establishing it as a mechanically and electrically tunable anisotropic 2D semiconductor.

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• Band gap
• Density of states
• Edge states
• Electronic structure of atoms & molecules
• Phase transitions by order
• Twistronics
• Twisted bilayers
• Two-dimensional electron system
• First-principles calculations