Ernst Heinrich Oskar Kasimir Weinschenk (6 April 1865, Esslingen am Neckar – 26 March 1921, Munich) was a German mineralogist and petrologist.

His scientific research included mineralogical analysis of meteorites, and studies of contact-metamorphic mineralization in the Alpine region of central Europe.

[1] Weinschenk's Grundzüge der Gesteinskunde was translated into English in 1916 by Albert Johannsen as "The fundamental principles of petrology".

With mineralogist Konrad Oebbeke (1853–1932), he published editions 6 (1899) & 7 (1913) of Wolfgang Franz von Kobell's Lehrbuch Der Mineralogie : in leichtfasslicher Darstellung.

Other works by Weinschenk include: The mineral weinschenkite, also known as "churchite-(Y)", is named after him.