Lanthanum tellurites, La₂Te₃O₉ and La₂Te₄O₁₁, have been prepared by the solid state synthesis route and characterized for their phase and chemical compositions by XRD and ICP-AES analyses. The molar enthalpies of solution of La₂Te₃O₉(s), La₂Te₄O₁₁(s), La₂O₃(s) and TeO₂(s) in 0.150 dm³ of 10.98 mol dm³ HCl were measured using an isoperibol calorimeter. From these results and other auxiliary data the standard molar enthalpy of formation of La₂Te₃O₉(s) and La₂Te₄O₁₁(s) were derived to be (2814.6 ± 12.9) kJ mol^-1 and (3116.5 ± 17.3) kJ mol^-1, respectively, at 298.15 K which are the first reported thermodynamic data on these compounds at 298.15 K.