<p>A novel strategy was proposed to produce chemically heterogeneous bainite in low-carbon ultrafine bainitic steel, utilizing compositionally partitioned pearlite as the initial microstructure combined with rapid heating and austempering. The effects of chemical heterogeneity on the transformation–microstructure–property relationships of ultrafine bainitic steel were investigated. Results indicated that chemically heterogeneous high-temperature austenite inherited from Mn/Cr-partitioned pearlite was preserved through rapid heating, which significantly improved the bainitic transformation kinetics. This acceleration primarily stemmed from the increased phase transformation driving force and reduced nucleation activation energy in Mn/Cr-depleted regions, alongside the enhanced carbon diffusivity resulting from the chemically heterogeneous microstructure featuring alternating distributed Mn/Cr-enriched and depleted regions. The chemically heterogeneous bainite ultimately exhibited a pearlite-like morphology, consisting of bainitic ferrite lath and filmy retained austenite with pronounced Mn/Cr variations. Introducing Mn/Cr heterogeneity into chemically heterogeneous bainite could promote bainite sheaves refinement, reduce the quantity and size of blocky retained austenite and elevate the proportion of filmy retained austenite. Grain boundary strengthening from refined bainitic ferrite laths increased yield strength by ~ 180&#xa0;MPa. Meanwhile, the predominantly filmy microstructure with finely dispersed blocky retained austenite enhanced post-uniform elongation, reflecting the improved local formability. These findings provide theoretical guidance for developing low-carbon ultrafine bainitic steel with controlled chemically heterogeneous, enabling shortened processing cycles and superior strength–toughness synergy.</p>