Abstract: The hot deformation behaviours of 316LN-Mn austenitic stainless steel were investigated by uniaxial isothermal compression tests at different temperatures and strain rates. The microstructural evolutions were also studied using electron backscatter diffraction. The flow stress decreases with the increasing temperature and decreasing strain rate. A constitutive equation was established to characterize the relationship among the deformation parameters, and the deformation activation energy was calculated to be 497.92 kJ/mol. Processing maps were constructed to describe the appropriate processing window, and the optimum processing parameters were determined at a temperature of 1107–1160°C and a strain rate of 0.005–0.026 s⁻¹. Experimental results showed that the main nucleation mechanism is discontinuous dynamic recrystallization (DDRX), followed by continuous dynamic recrystallization (CDRX). In addition, the formation of twin boundaries facilitated the nucleation of dynamic recrystallization.