In this work, the compound 1,2-dibora-4-gallatacyclopentane anion was obtained from the reaction of the dilithium salt of 2,3-diboratabutadiene with "Ga2I3." It was fully characterized by 11B, 1H, and 13C NMR spectroscopy and single-crystal X-ray diffraction analysis. The geometry of this five-membered ring shows Ga-C-B angles of approximately 95.1(3)°, which are about 9.3° smaller than those in carbon-based cyclopentane with 104.4(2)°. In addition, the torsion angle C-B-B-C is 60.3(5)°, about 46° larger than that in cyclopentane with 14.4(2)°. The distorted, nonplanar structure of the five-membered ring is due to the interactions between the σ(Ga-C) bonds and the empty p-orbitals of the boron atoms.