Jakob Rosanes (August 16, 1842 Brody, Austria-Hungary (now Ukraine) – January 6, 1922) was a German mathematician who worked on algebraic geometry and invariant theory. He was also a chess master.

Rosanes studied at University of Berlin and the University of Breslau. He obtained his doctorate from Breslau (Wrocław) in 1865 and taught there for the rest of his working life. He became professor in 1876 and rector of the university during the years 1903 – 1904.

Rosanes made significant contributions in Cremona transformations.