The hexanitratolanthanate anion (La(NO3)63−) is an interesting symmetric anion suitable to construct the component of water‐free rare‐earth‐metal ionic liquids. The syntheses and structural characterization of eleven lanthanum nitrate complexes, [Cnmim]3[La(NO3)6] (n=1, 2, 4, 6, 8, 12, 14, 16, 18), including 1,3‐dimethylimidazolium hexanitratolanthanate ([C1mim]3[La(NO3)6], 1), 1‐ethyl‐3‐methylimidazolium hexanitratolanthanate ([C2mim]3[La(NO3)6], 2), 1‐butyl‐3‐methylimidazolium hexanitratolanthanate ([C4mim]3[La(NO3)6], 3), 1‐isobutyl‐3‐methylimidazolium hexanetratolanthanate ([isoC4mim]3[La(NO3)6], 4), 1‐methyl‐3‐(3′‐methylbutyl)imidazolium hexanitratolanthanate ([MC4mim]3[La(NO3)6], 5), 1‐hexyl‐3‐methylimidazolium hexanitratolanthanate ([C6mim]3[La(NO3)6], 6), 1‐methyl‐3‐octylimidazolium hexanitratolanthanate ([C8mim]3[La(NO3)6], 7), 1‐dodecyl‐3‐methylimidazolium hexanitratolanthanate ([C12mim]3[La(NO3)6], 8), 1‐methyl‐3‐tetradecylimidazolium hexanitratolanthanate ([C14mim]3[La‐(NO3)6], 9), 1‐hexadecyl‐3‐methylimid‐azolium hexanitratolanthanum ([C16dmim]3[La(NO3)6], 10), and 1‐methyl‐3‐octadecylimidazolium hexanitratolanthanate ([C18mim]3[La(NO3)6], 11) are reported. All new compounds were characterized by 1H and 13C NMR, and IR spectroscopy as well as elemental analysis. The crystal structure of compound 1 was determined by using single‐crystal X‐ray diffraction, giving the following crystallographic information: monoclinic; P21/c; a=15.3170 (3), b=14.2340 (2), c=13.8954(2) Å; β=94.3453(15)°, V=3020.80(9) Å3, Z=4, ρ=1.764 g cm−3. The coordination polyhedron around the lanthanum ion is rationalized by six nitrate anions with twelve oxygen atoms. No hydrogen‐bonding network or water molecule was found in 1. The thermodynamic stability of the new complexes was investigated by using thermogravimetric analysis (TGA). The water‐free hexanitratolanthanate ionic liquids are thermal and moisture stable. Four complexes, namely complexes 8–11, were found to be ionic liquid crystals by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). They all present smectic A liquid‐crystalline phase.