Theodor Heinrich Gottfried Keil (25 May 1822, Gressow – 27 August 1894, Friedrichroda) was a German classical philologist. He was a son-in-law to educator Friedrich August Eckstein (1810–1885). He studied classical philology at the Universities of Göttingen and Bonn, receiving his doctorate in 1843 with a textual critique on the Roman poet Propertius. From 1844 to 1846 he conducted manuscript studies at libraries in Italy. After his return to Germany, he became an instructor at the Francke Foundation Pädagogium in Halle an der Saale.