Abstract Optical absorption measurements are used to locate and assign 79 crystal-field (Stark) levels split out of the 4f 3 electronic configuration of Nd 3+ in single crystals of neodymium nonahydrate tris(trifluoromethanesulfonate), [Nd(H 2 O) 9 ](CF 3 SO 3 ) 3 , denoted hereafter as NdTRF. Line strengths are determined for 56 transitions between Stark levels. Single crystals of NdTRF have hexagonal, P6 3 /m(C 6h 2 ) space-group symmetry, and each Nd 3+ ion is coordinated to nine water molecules in a slightly distorted tri-capped trigonal prism structure of C 3h symmetry. The energy-level structure of 4f 3 (Nd 3+ ) in NdTRF is analyzed in terms of a model Hamiltonian that includes consideration of both one-electron crystal-field and two-electron correlation-crystal-field interactions, the latter interactions making important contributions to the energy-level structures of several 4f 3 [ SL ] J multiplet manifolds. Line strength data obtaibned for NdTRF is analyzed in terms of a general 4f → 4f transition intensity model in which the details of the 4f-electron/crystal-field/electric-dipolar radiation-field interactions are represented in parametric form. The derived parameters provide information about structural properties and interaction mechanisms that contribute to 4f → 4f transition intensities. The general crystal-field and intensity parameters are further analyzed in terms of a set of ‘intrinsic’ parameters that are related to contributions from individual Nd 3+ OH 2 pairwise interactions.