  We investigate Coherent Population Trapping in a strongly interacting
ultracold Rydberg gas. Despite the strong van der Waals interactions and
interparticle correlations, we observe the persistence of a resonance with
subnatural linewidth at the single-particle resonance frequency as we tune the
interaction strength. This narrow resonance cannot be understood within a
meanfield description of the strong Rydberg--Rydberg interactions. Instead, a
many-body density matrix approach, accounting for the dynamics of interparticle
correlations, is shown to reproduce the observed spectral features.
