The Dennis Otte Round Barn is a round barn in the U.S. state of Illinois near the unincorporated Stephenson County community of Eleroy. The barn was built in 1930 by Herman Altenbern and has a diameter of 54 feet (16.5 m). The barn is representative of the last round barn design variations that evolved. The Otte Round Barn was added to the U.S. National Register of Historic Places in 1984.