Jan Szczepan Otrębski (8 December 1889 – 26 April 1971) was a Polish philologist, linguist, and author of 350 scientific papers in the field of Slavic and Baltic studies. He is particularly noted for his study of the Lithuanian language. He held the Chair of Baltic Philology in the Adam Mickiewicz University in Poznań and was the founder of the Lingua Posnaniensis journal. His three-volume work Gramatyka języka litewskiego (Grammar of Contemporary Lithuanian) is considered his magnum opus.