  The Fermilab Tevatron (p pbar), operating at sqrt(s)=1.96 TeV, is a rich
source of B hadrons. The large acceptance in terms of rapidity and transverse
momentum of the charged particle tracking system and the muon system make the
upgraded Run II D0 detector an excellent tool for B physics. In this article,
we report on selected physics results based on the first 250 pb^-1 of Run II
data. This includes results on the X(3872) state, semileptonic B decays, B
hadron lifetimes, flavour oscillations, and the rare decay B_s -> mu^+ mu^-.
