The singlet ground state OBHe+((1)Sigma(+)) has been investigated at the B3LYP, CASSCF, MP2, CCD, and CCSD(T) levels of theory, with various basis sets. The ion results thermochemically stable with respect to dissociation into singlet ground state BO+((1)Sigma(+)) and He by nearly 25 kcal mol(-1). Apart from He-2(+), which requires ca. 57 kcal mol(-1) to dissociate into He+ and He, this is probably the largest presently known interaction energy between a ground state singly charged ion and a helium atom. The implications of our calculations for future gas-phase experiments are also briefly discussed. (C) 2004 Elsevier B.V. All rights reserved.