Johann Karl Thilo (Langensalza, near Erfurt, 28 November 1794 — Halle 17 May 1853) was a German theologian and biblical scholar.
He studied theology at the University of Leipzig and a final semester at the University of Halle, where he was appointed to teach at the preparatory Paedagogium of the Francke institutions, and assisted his father-in-law, Georg Christian Knapp, director of the theological seminary.
In 1820 he travelled to Paris, London and Oxford with his colleague Heinrich Friedrich Wilhelm Gesenius for the examination of rare Eastern manuscripts.
He is remembered for his planned series of editions of apocrypha, Codex Apocryphus Novi Testamenti of which the first volume appeared in 1832, which set a new standard in textual criticism in this field.
Thilo managed to stay apart from the theological disagreements that divided Halle, remaining on cordial terms with members of both parties.