Jürgen Kurt Moser (July 4, 1928 – December 17, 1999) was a German-American mathematician, honored for work spanning over four decades, including Hamiltonian dynamical systems and partial differential equations.Moser completed his undergraduate education at and received his Dr. rer. nat. from the University of Göttingen in 1952, studying under Franz Rellich. After his thesis, he came under the influence of Carl Ludwig Siegel, with whom he coauthored the second and considerably expanded English language edition of a monography on celestial mechanics. Having spent the year 1953 at the Courant Institute of New York University as a Fulbright scholar, he emigrated to the United States in 1955 becoming a citizen in 1959.[