<p>Understanding the causes and magnitude of the yield gap is crucial for developing strategies to enhance maize productivity in a sustainable manner. The current research focused on assessing the maize yield gap in 12 maize-producing regions across three provinces of Iran using a modeling approach. Results revealed that, at the national scale, the total yield gap (YG) was 35% (3.38 t ha⁻¹), indicating that the maize grain yield achieved by farmers was only 65% of the attainable yield over the past three decades. The largest proportion of the YG was attributed to the yield gap due to improper nitrogen limitation (YG_N), which accounted for 34.4%, followed by the yield gap due to improper sowing date (YG_S) at 33.1%, the yield gap due to water limitation (YG_W) at 8%, and the yield gap due to other limiting and reducing factors (YG_O) at 11.4%. However, the relative contributions of YG_N, YG_S, YG_W, and YG_O to the total YG varied by region. In hot regions, YG_S represented the largest share of the yield gap, accounting for 66.6%. The influence of inappropriate nitrogen application on the yield gap was particularly pronounced in the western regions, where YG_N accounted for 52.7% of the YG, compared to only 16.7% in the southwestern regions. Additionally, YG_W was most significant in the western regions. Overall, our results demonstrate significant potential for improving maize production in Iran. Adjusting sowing dates in hot regions and optimizing irrigation in the western areas present substantial opportunities to close the yield gap and boost maize productivity.</p>