For an ultra-dense exciton gas in cuprous oxide (Cu$_2$O), exciton-exciton interactions are the dominant cause of exciton decay. This study demonstrates that the accepted Auger recombination model overestimates the exciton decay rate following intens
e two photon excitation. Two exciton decay is relevant to the search for collective quantum behavior of excitons in bulk systems. These results suggest the existence of a new high density regime of exciton behavior.