**Otto Marcin Nikodym** (3 August 1887 – 4 May 1974) was a Polish mathematician. He was educated at the Universities of Lwow and Warsaw, and the Sorbonne. Nikodym taught at the Universities of Kraków and Warsaw and at the Akademia Górnicza in Kraków. He came to the United States in 1948 to join the faculty of Kenyon College. He retired in 1966 and moved to Utica, N.Y., where he continued his research.

Nikodym worked in a wide range of areas, but his best-known early work was his contribution to the development of the Lebesgue–Radon–Nikodym integral (see Radon–Nikodym theorem). His work in measure theory led him to an interest in abstract Boolean lattices. His work after coming to the United States centered on the theory of operators in Hilbert space, based on Boolean lattices, culminating in his *The Mathematical Apparatus for Quantum-Theories*. He was also interested in the teaching of mathematics.