  We present the first XMM-Newton observations of the radio-quiet quasar
MR2251-178. We model the X-ray spectrum with two power laws, one at high
energies with a slope of \Gamma=1.6 and the other to model the soft excess with
a slope of \Gamma=2.9, both absorbed by at least two warm absorbers (WAs). The
high-resolution grating spectrum shows emission lines from N VI, O VII, O VIII,
Ne IX, and Ne X, as well as absorption lines from the low ionization ions O
III, O IV, and O V. A study of the spectral variations in MR2251-178 over a
period of 8.5 years yields that all X-ray observations can be fitted with the
above model. Luminosity variations over timescales of years seem to correlate
with the soft excess variations but not with the WA properties variations. The
overall picture is that of a stratified WA that enters and disappears from the
line-of-sight on timescales of several months. We also present the first FUSE
spectrum of MR2251-178. The general characteristics of the UV and X-ray
absorbers seem to be consistent.
