Abstract Relativistic Multi-Reference Møller-Plesset (MR-MP) many-body perturbation theory calculations are reported for the ground and excited states of Fe viii. Energies are provided for states coming from the configurations (l = s, p, d, and f) with , p ≤ 3, and q ≤ 1. The MR-MP results were compared with the recommended observed values in the CHIANTI-v8 database and with previous ab-initio calculations. The MR-MP calculations reproduce 90% of the available observed values within 3500 cm−1. The previous accurate ab-initio calculations reproduce only 50% of the observed values within 3500 cm−1. The electronic structure of Fe viii is very complex and our MR-MP results show that accurate calculations require the inclusion of not only 3s 2–3d 2, 3p 2–3d 2, and 3s3p–3d 2 promotions but also of all electron correlations via perturbation theory.