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.
The Dennis Otte Round Barn is one of 31 round barns that were constructed in a four county area, the Stephenson County area, that includes Winnebago County, Stephenson County and Rock and Green Counties in Wisconsin. Twenty one of those barns, including the Otte Round Barn are within Stephenson County.
While the design of the Otte Round Barn is consistent with the designs found during the second phase of Stephenson County, Illinois round barn construction it does have key differences which set it apart from other similar barns. Similarities are found in the single hip roof, the squat cupola and the special rafter bracing technique. The use of salvaged materials reflects the Depression era economy during which the Otte Round Barn was constructed. These characteristic reflect the last design variation found in Stephenson County round barns. The Otte Round Barn was added to the U.S. National Register of Historic Places on February 23, 1984 as part of a Multiple Property Submission.