  We have analyzed recently published XENONnT data for the spontaneous X-ray
emission signature predicted by the objective wave function collapse model of
quantum mechanics. With extremely low background and large exposure, XENONnT
data can be used to completely exclude the theoretically predicted collapse
parameters of continuous spontaneous localization~(CSL) model suggested by
Ghirardi, Rhimini and Weber. Our result strongly suggests that the simplest
version of the CSL model with the white-noise assumption is unlikely to provide
answers to the long-standing measurement problem of quantum mechanics and
motivates pursuits of more complex versions of the theory. If the result is
interpreted with the Di\'{o}si-Penrose gravitational wave function collapse
model, our limit improves the previous limit by a factor of 5.7. Detailed
analysis using more precise background modelling can further improve the
limits.
