We present the results of rotational coherence spectroscopy (RCS) experiments on jet-cooled naphthalene trimer. The RCS results, obtained by mass-selective, time-resolved ionization depletion, indicate that the species is an oblate symmetric top with rotational constants B = 167 +/- 1 MHz and C = 141 +/- 1 MHz. These constants are consistent with a cluster in which the long axes of three cyclically-arranged, symmetrically equivalent naphthalene moieties are parallel to one another and to the symmetry axis of the cluster. The distances between the centers of mass of the moieties in this structure are determined to be 4.925 +/- 0.020 Angstrom from the rotational constants. The results are consistent with ab initio and empirical force-field calculations of the species＇ structure (see Gonzalez and Lim, preceding Letter) and with the results of prior vibrational and vibronic spectroscopic studies.