Thermoanalytical and crystal growth investigations of the ternary system Cs2O-Li2O-Nb2O5 are presented in order to grow stoichiometric LiNbO3 (LN) crystals. Part of the phase diagram is determined and subsolidus phases are identified at room temperature by X-ray powder diffraction. Among the constituent phases, a new tetragonal cesium lithium niobate phase is assessed. From the Cs2O-Li2O-Nb2O5 system, good quality quasi-stoichiometric LN crystals can be grown.