The title compound, (C8H15N2)[LaCl4(CH3OH)(C3H7OH)], consists of one 1-butyl-3-methylimidazolium (BMI+) cation and one hexahedral tetrachlorido(methanol)(propan-2-ol)lanthanate anion. The LaIII ion is eight-coordinate, with the LaIII ion bridged by a pair of Cl atoms, so forming chains propagating along the a-axis direction. Each LaIII ion is further coordinated by two isolated Cl atoms, one methanol and one propan-2-ol molecule. The coordinated methanol and propan-2-ol molecules of the anion form O—HCl hydrogen bonds with the Cl atoms of inversion-related anions. The BMI+ cation froms C—HCl hydrogen bonds with the Cl atoms of the anion. The anions are located in the C faces of the triclinic unit cell, with an inversion center in the middle of the La2Cl2 ring of the polymeric chain.