Johann Nepomuk Sepp (7 August 1816 – 5 June 1909) was a German historian and politician, and a native of Bavaria.
Johann Nepomuk Sepp was born the son of a tanner and dyer in Bad Tölz, Bavaria. He studied philosophy and Catholic theology, law, philology and history in Munich, 1834-1836 and 1837-1839. In 1836, he interrupted his university studies for a trip to Switzerland and Italy, after which he entered the Gregorianum seminary in Munich. In 1839 he was awarded a Ph.D., and established himself as a private scholar in Bad Tölz. From 1844 to 1846 he taught as lecturer at the University of Munich.
After he had traveled to Syria, Palestine and Egypt in 1845 and 1846, he was appointed assistant professor in Munich in 1846, but was dismissed in 1847, along with seven of his colleagues, as a result of their involvement in opposition to the elevation of Lola Montez, mistress of Ludwig I of Bavaria, to the nobility. Sepp had his teaching qualification withdrawn and was banished from the Bavarian capital.
In 1848 he was elected to the Frankfurt National Assembly, and in 1849 to the Bavarian Chamber of Representatives. In 1850, after the resignation of King Ludwig I of Bavaria, Sepp was rehabilitated, and in 1850-1864 and 1864-1867 was Associate Professor of History in Munich. In 1861 he bought the partially destroyed Wessobrunn Abbey, which was then being used as a quarry, in order to preserve it for posterity.
Sepp retired suddenly in December 1867 "for personal reasons". He was appointed to the Zollparlament in 1868, and in 1869 again elected to the Bavarian Chamber, where he was one of the most influential representatives of the German national cause during the critical period between 1870 and 1871. In 1872, he undertook a new journey to Palestine on behalf of the new German Empire.
Sepp was highly literate and a capable publicist. He was sometimes prone to original and idiosyncratic interpretations of history, so was respectfully nicknamed by colleagues "die umgestürzte Bücherkiste" ("the overturned bookcase"). His final major work, his contribution to German folklore, appeared in 1890: "The Religion of the Ancient Germans. Their continued existence in folk tales, processions and festivities to the present". This was a kind of view in hindsight, a compressed, comparative survey of a lifetime of accumulated and processed historical anthropological and religious knowledge; like most of his works, it has not enjoyed a new edition. Still frequently cited today is his study of the myths, legends, customs and manners of Bavaria, the Altbayerischer Sagenschatz of 1876. This work, although heavily compressed and eclectic, attempted an overview of the mythology of Bavaria, with literary references. Sepp also published under the pseudonym "Eusebius Amort der Jüngere".