Schur's lemma (disambiguation)

At least three well-known results in mathematics bear the name Schur's lemma:
 * Schur's lemma from representation theory
 * Schur's lemma from Riemannian geometry
 * Schur's lemma in linear algebra says that every square complex matrix is unitarily triangularizable, see Schur decomposition
 * Schur test for boundedness of integral operators