Ultrafaint dwarf galaxies (UFDs) are ideal for studying dark matter (DM) due to minimal baryonic effects. UFD observations suggest cored DM profiles. We find that the core radius–stellar mass scaling predicted by fuzzy dark matter (FDM) is at 6.1σ-sigma tension with UFD observations. Combining observations from 27 UFDs, the required FDM mass ma=3.2-0.6+0.8×10-21eV is also in conflict with existing Lyman-alpha bounds. Our results suggest that FDM cannot provide a consistent explanation for DM cores and imply ma>2.2×10-21eV at to 2-sigma CL.