The structural, mechanical and elastic properties of industrially important Ctype lanthanide sesquioxides, Ln₂O₃ (Ln=Pm, Sm, Eu, Gd, Tb, Dy), are studied by employing ab initio electronic structure calculations. The calculated lattice parameters for Ln₂O₃ match very well with the experimental crystal structures and clearly reproduce the lanthanide contraction across the lanthanide series. Similarly, the elastic constants, bulk modulus and other mechanical properties obtained from our calculations are in very good agreement with the values available in the literature. The knowledge about bulk modulus and shear modulus could provide the volume and shape variation of material with respect to external strain which has significant impact for selecting suitable materials for novel applications.