  The quasi-bound states of charged massive scalar fields in the near-extremal
charged Reissner-Nordstr\"om black-hole spacetime are studied {\it
analytically}. These discrete resonant modes of the composed black-hole-field
system are characterized by the physically motivated boundary condition of
ingoing waves at the black-hole horizon and exponentially decaying (bounded)
radial eigenfunctions at spatial infinity. Solving the Klein-Gordon wave
equation for the linearized scalar fields in the black-hole spacetime, we
derive a remarkably compact analytical formula for the complex frequency
spectrum which characterizes the quasi-bound state resonances of the composed
Reissner-Nordstr\"om-black-hole-charged-massive-scalar-field system.
