To explore the family of 2D intrinsic antiferromagnetic materials, Mn-based two-dimensional transition metal borides (known as MBenes) were studied using first-principles calculations. MBenes with a general formula of Mn_n+1B_2n (n = 1–3) were designed from their bulk counterparts known as MAB phases, and they were found to possess good thermodynamical, mechanical and dynamical stabilities. Within the DFT+U approach, Mn₂B₂, Mn₃B₄ and Mn₄B₆ exhibit an orthorhombic structure and C-type antiferromagnetic ground state. Studied MBenes show a metallic nature with average atomic magnetic moments of 3.13, 2.67 and 2.74μ_B/Mn-atom, respectively, at the Mn site. The Mn atom in Mn₂B₂ exhibited a trigonal prismatic symmetry, while in the case of Mn₃B₄ and Mn₄B₆, two different Mn atoms with trigonal prismatic and octahedral symmetries were found. The calculated Néel temperatures for Mn₂B₂, Mn₃B₄ and Mn₄B₆ were 934.08 K, 1317.61 K and 2177.19 K, respectively. The sizable values of magnetic exchange interactions of these MBenes up to their fifth nearest neighbour shows the potential of these unexplored 2D materials towards antiferromagnetic spintronics.