The great nineteenth-century mathematician Peter Gustav Lejeune Dirichlet (1805-59) studied in Paris, coming under the influence of scholars including Fourier and Legendre. He then taught at Berlin and Goettingen universities, where he was the successor to Gauss and mentor to Riemann and Dedekind. His achievements include the first satisfactory proof of the convergence of Fourier series under appropriate conditions, and the theorem on primes in arithmetic progression which was, at the same time, the foundation of analytic number theory and one of its greatest achievements. He also did important work on Laplace’s equation, the theory of series and many other topics. This two-volume collection of his works, published 1889-97, was compiled by Leopold Kronecker (1823-91). Volume 2 was completed by Lazarus Fuchs (1833-1902) and contains Dirichlet’s publications from 1844 onwards, together with some unpublished papers and selected correspondence with Gauss, Alexander von Humboldt and Kronecker.