  We present a calculation of the mass spectrum of positronium within the
framework of the recently developed Basis Light-Front Quantization approach to
non-perturbative quantum field theory. In this calculation, we employ a
two-body effective interaction for the photon exchange, neglecting self-energy
effects. We demonstrate the cancellation of Light-Front small-{\it x}
divergences within our non-perturbative approach. The resulting spectrum is
compared to both non-relativistic quantum mechanics and previous work in
Discretized Light-Cone Quantization.
