Unmet need for family planning contributes to unintended pregnancies, unsafe abortions, and preventable maternal and child deaths, and remains high in sub-Saharan Africa. In Zambia, national estimates may conceal important geographic inequalities. We assessed the spatial distribution of, and factors associated with, unmet need for family planning among women of reproductive age in Zambia. We conducted a cross-sectional analysis of the 2024 Zambia Demographic and Health Survey (ZDHS), including 12,133 women aged 15-49 years. Survey-weighted logistic regression, accounting for the stratified two-stage cluster design, was used to estimate adjusted odds ratios (AOR) with 95% confidence intervals (CI). Global spatial autocorrelation was assessed with Morans I, local hotspots with the Getis-Ord Gi* statistic, and spatial clusters with a purely spatial Bernoulli scan statistic in SaTScan. The weighted prevalence of unmet need was 27.0% (95% CI: 25.7-28.3%), ranging from 23.8% in Central to 31.6% in North-Western Province. Unmet need was spatially clustered (Morans I = 0.142, p = 0.018), with hotspots mainly in Lusaka, Southern, North-Western, and Northern provinces; SaTScan detected a primary cluster in Lusaka (observed-to-expected ratio 1.42, p < 0.001). Women in union (AOR 2.33, 95% CI: 1.90-2.86) and never-married women (AOR 2.20, 95% CI: 1.69-2.86) had higher odds of unmet need than formerly married women, as did women with five or more children compared with none (AOR 3.05, 95% CI: 2.25-4.13). Lower odds were observed among women aged 35-49 years (AOR 0.65, 95% CI: 0.52-0.83), women in the richest wealth quintile (AOR 0.62, 95% CI: 0.45-0.86), employed women (AOR 0.73, 95% CI: 0.64-0.84) and urban residents (AOR 0.80, 95% CI: 0.68-0.95). Unmet need for family planning in Zambia is high, geographically clustered and socially patterned. Family planning programmes should prioritise hotspot areas, particularly Lusaka, Southern and North-Western provinces, while targeting younger, higher-parity and poorer women.