Walter Gordon (13 August 1893 – 24 December 1939) was a German theoretical physicist.
Walter Gordon was the son of businessman Arnold Gordon and his wife Bianca Gordon (nee Brann). The family moved to Switzerland in his early years. In 1900 he attended school in St. Gallen and in 1915 he began his studies of mathematics and physics at University of Berlin. He received his doctoral degree in 1921 from Max Planck. In 1922, while still at the University of Berlin, Gordon became the assistant of Max von Laue. In 1925, he worked for some months in Manchester with William Lawrence Bragg and later, at the Kaiser Wilhelm Society for fiber chemistry in Berlin. In 1926 he moved to Hamburg, where he attained the habilitation in 1929. In 1930 he became a professor. He married a local Hamburg woman, Gertrud Lobbenberg, in 1932. He moved to Stockholm in 1933 because of the political situation in Germany. While at the university he worked on mechanics and mathematical physics.
Oskar Klein and Walter Gordon proposed the Klein–Gordon equation to describe quantum particles in the framework of relativity. Another important contribution by Gordon was to the theory of the Dirac equation, where he introduced the Gordon decomposition of the current into its center of mass and spin contributions, and so helped explain the g-factor value in the electron's gyromagnetic ratio.