<p>This study investigates the fertility gap in South Korea, defined as the discrepancy between the ideal and actual number of children. Using data from the 2021 Family and Fertility Survey, the analysis focused on 2217 married women aged 40 and older who reported no further childbearing intentions, thereby representing women who had completed their reproductive trajectories. Results indicate that while the average ideal number of children was 2.02, the actual average was 1.68, revealing a persistent shortfall between fertility aspirations and outcomes. Multinomial logistic regression showed that insufficient fertility was more common among women with lower incomes and those assigning high emotional or economic value to children, whereas stronger endorsement of patriarchal gender roles was associated with a lower likelihood of insufficient fertility. By contrast, excessive fertility intention was linked to stronger endorsement of individualistic family values, lower emotional valuation of children, and was less likely among economically active women. Taken together, the results highlight a paradox: the same structural and cultural forces that constrain some women from meeting their fertility ideals may also lead others to exceed them. This paradox underscores the limited autonomy and institutional support available for women to realize their reproductive goals. The study concludes that integrated policy measures—combining economic support, gender equality initiatives, and family planning services—are essential to narrow the fertility gap and address South Korea’s demographic challenges.</p>