A C T Food insecurity (FI) is associated with increased mortality risk, depression, and obesity in females in high-income countries, but causal mechanisms remain unclear. FI is often assumed to lead to increased levels of hunger. However, quantitative evidence describing daily experiences of hunger in FI is lacking. Our pre-registered study used ecological momentary assessment to capture experiences of hunger in two groups of UK-based females: those experiencing FI (N = 143) and those experiencing food security (FS; N = 149). Participants self-reported hunger hourly (0900-2100) for one week (Monday-Sunday). There was no difference between groups in mean hunger (t(290) = 0.17, p = .866, d = 0.02) nor within-day standard deviation in hunger (t(290) = 1.31, p = .193, d = 0.15). However, both quantities fluctuated more from day to day in the FI group. Compared to the FS group, participants in the FI group had a larger day-to-day variation in mean hunger (t(284) = 2.43, p = .016, d = 0.29) and a larger day-to-day variation in the within-day standard deviation of hunger (t(284) = 2.90, p = .004, d = 0.34). In exploratory analyses, we found that the hunger of the two groups patterned differently across the day. Our findings suggest that experiences of hunger are less stable in those experiencing FI, which may reflect associations between FI and greater uncertainty in food access, higher variability in meal timings or the increased likelihood of chaotic home and work lives.