Leon Kellner (Hebrew: ליאון קלנר; 17 April 1859 – 5 December 1928) was an English lexicographer, grammarian, and Shakespearian scholar.

Kellner travelled to London in 1887 where the Early English Text Society invited him to translate William Caxton's Blanchardyn and Eglantine.

Then in 1890 Kellner received his habilitation after publishing a thesis based on original research titled Caxton's Syntax and Style.

Kellner dedicated his translation of Caxton and his habilitation thesis to Frederick James Furnivall, founder of the Early English Text Society.

After the war, Kellner served as a translator in the office of the President of the Austrian Republic and lectured at the Technical University of Vienna.