The new compounds La 4 Ti 2 O 4 Se 5 and La 6 Ti 3 O 5 Se 9 have been obtained from stoichiometric reactions of La, Ti, TiO 2 , and Se in fused-silica tubes at 1223 K. Potassium halide 6uxes were used to promote the crystallization. The compounds have been characterized by single-crystal X-ray di4raction methods. La 4 Ti 2 O 4 Se 5 crystallizes in the orthorhombic space group Cmcm with eight formula units in a cell at 153 K of dimensions a β«Ψβ¬ 3.9695(4) A > , b β«Ψβ¬ 33.115(3) A > , c β«Ψβ¬ 18.6380(18) A > . The 5ve independent La atoms in the structure are found in four di4erent coordination polyhedra, namely tricapped trigonal prism, bicapped trigonal prism, square antiprism, and 7-octahedron, whereas the three independent Ti atoms have octahedral coordination. The crystal structure comprises in5nite layers that stack along the b-axis. Two adjacent layers are linked by La+Se bonds. La 4 Ti 2 O 4 Se 5 represents the 5rst rare-earth titanium oxychalcogenide containing only Ti 3Ψ cations. La 6 Ti 3 O 5 Se 9 crystallizes in the monoclinic space group C2/m with four formula units in a cell at 153 K of dimensions a β«Ψβ¬ 43.999(6) A > , b β«Ψβ¬ 3.9454(6) A > , c β«Ψβ¬ 11.1093(16) A > , β«Ψβ¬ 96.882(2)3. The six independent La atoms in the structure are found in three di4erent coordination polyhedra, namely tricapped trigonal prism, bicapped trigonal prism, and 7-octahedron. The four independent Ti atoms have octahedral coordination. The crystal structure comprises in5nite condensed layers of composition 2 R [La 2 Ti 1 O 2 Se 3 ] that stack successively with extended slabs of composition 2 R [La 4 Ti 2 O 3 Se 6 ] along the a-axis. La 6 Ti 3 O 5 Se 9 is a mixed-valence compound in which two-thirds of the Ti cations are Ti 3Ψ and one-third are Ti 4Ψ .