<p>A hot-forged Fe-30Mn-11Al-1C-10Ni (wt.%) low-density steel was developed, possessing a comparable strength–ductility synergy to those subjected to prior cold rolling and aging treatment. The initial microstructure after hot forging contained austenite matrix (~ 70 vol.%) and a large fraction of B2 phases (~ 30 vol.%) owing to the addition of high content of Al and Ni. The resultant dual-phase morphology effectively blocked the grain growth during hot forging, resulting in extremely fine grain size of both austenite (&lt; 3&#xa0;μm) and B2 phases (&lt; 2&#xa0;μm). In addition, dual precipitation of nano-sized <i>κ</i>-carbides and DO₃ particles was formed during air cooling within austenite and B2 grains, respectively. Consequently, an excellent combination of strength (yield strength of 1250&#xa0;MPa, ultimate tensile strength of 1381&#xa0;MPa) and ductility (total elongation of ~ 25%) was achieved in the hot-forged specimens owing to the synergy of the multiple strengthening mechanisms and excellent strain hardening capability. Particularly, the sequentially activated slip-band refinement in austenite and B2 phases and the hindering effect on dislocation movement of B2 phase provided a consistently high strain hardening rate, contributing to the superior strength–ductility balance. However, further aging treatment resulted in a gradual increase in strength but a severe loss in ductility, due to the formation of coarse intergranular <i>κ</i>-carbides. The present study suggests that an excellent strength–ductility synergy in Ni-alloyed low-density steel could be achieved through simple hot forging followed by air cooling.</p> Graphical abstract <p></p>