The Museum of Slavonia is one of the oldest, with the size of the fundus and the most important museums in Croatia. It was founded in 1877 as "The Museum of the Free and Royal City of Osijek", with the donation of a wealth of money collections, arms and medals of the Osijek wholesaler and collector of antique Franjo Sedlaković.
At the beginning, the museum had a predominantly archeological and numismatic orientation (similar to other museums in these European regions of those years). In 1888 the museum was moved to a newly built Royal Kingdom building and located in two rooms.
The Museum of Slavonia in Osijek was founded in 1877 as the Museum of the Free and Royal City of Osijek. Founded over a donation of over two thousand items exhibited in the two showcases of the Hall of the City Hall sessions, over time, with almost half a million items, it became the largest complex museum in the Republic of Croatia, which has a national status since 1994.