Jacob Robert Emden (March 4, 1862 – October 8, 1940) was a Swiss astrophysicist and meteorologist.
Emden was born in St. Gallen, Switzerland. In 1907 he became associate professor of physics and meteorology at the Technical University of Munich. The same year he published the classic work, Gaskugeln: Anwendungen der mechanischen Wärmetheorie auf kosmologische und meteorologische Probleme (Gas balls: Applications of the mechanical heat theory to cosmological and meteorological problems), which provided a mathematical model as a basis of stellar structure. By 1920 he was a member of the Bayerische Akademie der Wissenschaften.
Emden served as the editor of Zeitschrift fur Astrophysik, founded in 1930. In 1933 he fled from Germany to escape the rise of the National Socialist party, returning to his native Switzerland.
He was the uncle of the German American astrophysicist Martin Schwarzschild by marriage to Karl Schwarzschild's sister. Jacob Robert Emden died in Zürich in 1940.
The crater Emden on the Moon is named after him. The Lane-Emden equation is named for him and Jonathan Homer Lane.