THE NATURAL CLASSIFICATION OF REAL LIE ALGEBRAS M. Rainer and H.-J. Schmidt Key words: Real Lie algebras, homogeneous Riemannian manifolds, general topology 1991 Math. Subject Classification: 53B20, 22E15. Abstract: We classify the $n$-dimensional real Lie algebras according to algebraic, geometric, and topological points of view. For the case that Lie algebra, Riemannian geometry, and general topology yield the same classification we call it the natural one. It turns out that for dimension $n\leq 3$ our classification is natural. For $n\geq 4$ partial results are given.