Singly charged rare gas borynium ions were prepared for the first time by making use of mass-selected ion/molecule reactions in a triple-quadrupole mass spectrometer. Halogen for rare-gas exchange reactions leading to the formation of the novel species BAr+, BKr+, and BXe+ were carried out by allowing the radical cation BBr+. to react with neutral rare gas atoms in the second quadrupole under conditions typically used for collision-induced dissociation (CID) in tandem mass spectrometry experiments. The ions formed contain the bonds B-Ar, B-Kr, and B-Xe, the lengths of which were calculated at the B3-LYP/LANL2DZ level of theory to be 2.590, 2.635, and 2.713 Angstrom, respectively. Natural bond orbital (NBO) population analysis revealed that the bond order increases with increasing size of the rare gas atom: Ar < Kr < Xe. The reactions leading to the formation of the singly charged boron cations of Ar, Kr, and Xe are endothermic by 50.1, 45.8, and 38.7 kcal/mol, respectively. The energy required to drive these reactions is supplied by the collision energy. The BX+ products formed are 7.2, 11.5, and 18.5 kcal/mol more stable than the separated B+ ion and the neutral rare gas X atom (= Ar, Kr, Xe, respectively).