Thomas Christian Tychsen (8 May 1758, Horsbüll – 23 October 1834, Göttingen) was a German orientalist and Lutheran theologian. He is known for his 1823 grammar of the Arabic language.
He studied theology and philology in Kiel and Göttingen, followed by an educational tour through Europe; France, Spain and Lombardy, completed with a lengthy stay in Vienna. In 1788, he became a full professor of theology at the University of Göttingen. He was a full member of the Göttingen Academy of Sciences and was associated with several foreign scientific societies.
He was the author of a book on Arabic grammar, Grammatik der arabischen Schriftsprache (1823), and edited works of the Greek poet Quintus Smyrnaeus. Among his better known students were Orientalists Wilhelm Gesenius (1786-1842) and Heinrich Ewald (1803-1875).