<p>Currently, the development of high-efficiency two-dimensional (2D) transistors is still hindered by the limited availability of suitable semiconductors and the contact resistance between the metal contact and the 2D semiconductors. Endeavors to address these challenges are highly desired. In this study, we conducted a comprehensive exploration of the potential 2D transition metal dinitrides (TMN₂s, TM = all the 3d, 4d and 5d transition metals) with hexagonal (h-) and trigonal (t-) phases through systematic first-principles calculations. Among all h-TMN₂s and t-TMN₂s structures, we identified 8 TMN₂s that exhibit dynamical and thermal stability at room temperature. Of these, the h–TiN₂, h–ZrN₂ and h–HfN₂ are found to be semiconductors, and their direct bang gap, calculated at the HSE06 level, are 1.48, 1.96 and 2.64&#xa0;eV, respectively. The electron and hole mobility (<i>μ</i>_e and <i>μ</i>_h) of these three structures exceed 1 × 10⁴ and 1 × 10³&#xa0;cm²·V⁻¹·s⁻¹, respectively. Especially, the <i>μ</i>_e of h–TiN₂ amounts to 2.5 × 10⁴&#xa0;cm²·V⁻¹·s⁻¹, and the <i>μ</i>_h of h-ZrN₂ reaches to 7.7 × 10³&#xa0;cm²·V⁻¹·s⁻¹. Importantly, unlike the MoS₂ system, h–TMN₂ forms Ohm contacts with both transition metals (e.g., Cu) and 2D metals (e.g., graphene), with tunneling possibilities exceeding 50% in the Cu system. These outstanding intrinsic semiconductor properties and contact characteristics exhibited by h–TMN₂ highlight the immense potential of transition metal dinitrides in driving the advancement of next-generation information devices. Our findings significantly broaden the range of 2D materials and provide valuable insights for the development of high-efficiency 2D information devices.</p> Graphical abstract <p></p>