The crystal structure of 3R-LiTiS2 was studied with combined experimental and theoretical approaches. The 3R polymorph of lithium titanium disulfide crystallizes rhombohedrally in the well-known NaCrS2 type with lattice parameters a = 352.98(1) pm, c = 1807.51(3) pm. The relative stability of 3R-LiTiS2 with respect to other known and hypothetical polymorphs was evaluated theoretically at DFT level employing the hybrid method B3LYP. 3R-LiTiS2 is less stable than the most common 1T phase (by 4 kJ·mol–1), and is more stable (by 5 kJ·mol–1) than the known phase c-LiTiS2 thus confirming the importance of this phase for further investigations.