Kaunas Maironis Academic Gymnasium, previously the Constituent Assembly Palace, is an historical building in Kaunas, Lithuania. The building was completed in 1862 and in 1863 the gymnasium was moved into it, but the building gained its greatest significance between 1920 and 1927 when the Constituent Assembly of Lithuania met there, as well as the interwar Seimas for its first three electoral periods. The Seimas was later moved to the newly built Palace of Justice and the Seimas.