In chemistry, a pentagonal bipyramid is a molecular geometry with one atom at the centre with seven ligands at the corners of a pentagonal bipyramid.

A perfect pentagonal bipyramid belongs to the molecular point group D5h.

The pentagonal bipyramid is a case where bond angles surrounding an atom are not identical (see also trigonal bipyramidal molecular geometry).

[1][page needed] This is one of the three common shapes for heptacoordinate transition metal complexes, along with the capped octahedron and the capped trigonal prism.

[2][3][page needed] Pentagonal bipyramids are claimed to be promising coordination geometries for lanthanide-based single-molecule magnets, since they present no extradiagonal crystal field terms, therefore minimising spin mixing, and all of their diagonal terms are in first approximation protected from low-energy vibrations, minimising vibronic coupling.