Oluf (Olaus) Gerhard Tychsen (December 14, 1734, Tondern, Denmark – December 30, 1815, Rostock, Germany) was a German Orientalist and Hebrew scholar. He is known today as one of the founding fathers of Islamic numismatics.
As a Protestant Christian, he attended secondary school in Altona and the Rabbinic school attached to the Altona synagogue. From 1756 he studied Oriental languages at the University of Halle.
He spent a year of missionary work towards the conversion of Jews, and then taught Hebrew in the newly founded University of Bützow. He held librarian and academic positions in Bützow. There he founded the Journal Buetzower Nebenstunden, which comprised a broad variety of articles about the Old Testament and Oriental Culture, especially material culture, such as Islamic coins.
From 1778 he taught at the University of Rostock. He worked in different fields of Oriental studies, Arabic, Syriac, and Hebrew. His Introduction into Islamic Numismatics, in 1794, was the first scientific handbook on this topic, based on twenty-seven years of research. Among his students were Christian Martin Frähn, later professor in Kazan and later founder of the Asiatic Museum in Saint Petersburg, and Christian Adler, who wrote the first scientific catalogue of a collection of Islamic coins and later became superintendent of Schleswig-Holstein. He was a prolific author who published some forty volumes of scholarly studies during his academic career. An interesting note is that he received rabbinic ordination. It is the only known case of it given to a non-Jew.