Otto Donner (15 December 1835, Kokkola – 17 September 1909, Helsinki) was a Finnish linguist and politician. He was professor of Sanskrit and Comparative Indo-European linguistics at the University of Helsinki, but also studied the Finno-Ugric languages. He was a member of the Diet of Finland 1877–1905, and minister of education 1905–1908. He was also influential in the founding of the Finno-Ugrian Society in 1883.
His mother tongue was Swedish, but he was a fennoman by conviction.
He is buried in the Hietaniemi Cemetery in Helsinki.