Define a topological Lie group to be a group object in the category of topological manifolds. Until stated otherwise G is assumed finite-dimensional. Theorem 1.1. LetG be a compact, simple Hausdorff group. Then eitherG is a finite simple group or it is Lie. The latter are much easier to classify: they are U(n), O(n), U(n,H) mod their centers, or one of five special cases (of dimensions ≤ 248), ...