In geometry, the pentagonal orthobirotunda is one of the Johnson solids (J34). As the name suggests, it can be constructed by joining two pentagonal rotundae (J6) along their decagonal faces, matching like faces. A 36-degree rotation of one rotunda before the joining, so that pentagons abut triangles and vice versa, yields an icosidodecahedron, one of the Archimedean solids.
The 92 Johnson solids were named and described by Norman Johnson in 1966.