Jakob Rosanes (also Jacob; 16 August 1842 – 6 January 1922) was a German mathematician who worked on algebraic geometry and invariant theory. He was also a chess master.

Jakob Rosanes
Jacob Rosanes
Born	16 August 1842 Brody, Austrian Empire
Died	6 January 1922 (1922-01-07) (aged 79) Breslau, Kingdom of Prussia
Nationality	German
Scientific career
Fields	Mathematics
Doctoral advisor	Heinrich Schröter
Doctoral students	Otto Toeplitz Ernst Steinitz

Rosanes was a grandson of Rabbi Akiva Eiger, one of the most revered Jewish religious scholars of the Talmud and halachic decisors of the 18th century. Eiger's daughter Baila was Rosanes' mother. Rosanes grew up during a period when the Enlightenment and increasing opportunities for social, academic and economic advancement for culturally assimilated Jews influenced large numbers of Jews to reconsider their faith. He was not religiously observant, and his children converted to Christianity.

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.^[1]

Rosanes made significant contributions in Cremona transformations.