The ternary title compound, dipotassium lanthanum penta-chloride, K(2)LaCl(5), is isotypic with Y(2)HfS(5) and various ternary rare-earth metal(III) halides with the general formula A(2)MX(5) (A = NH(4), In(I), Na-Cs; M = La-Dy; X = Cl-I). The La(3+) cations and three of the four symmetry-independent chloride anions are located on a crystallographic mirror plane. The La(3+) cations are surrounded by seven chloride anions, each in the shape of a monocapped trigonal prism, whereas the coordination spheres of the K(+) cations exhibit one more cap. Three of the four independent chloride anions reside in a fivefold cationic coordination, leading to distorted square pyramids. The fourth chloride anion has only four cationic neighbours, forming no specific polyhedron.