  Odderon is the C-odd amplitude which does not die out (or die very slowly)
with energy. We consider the constrains on the Odderon properties and the
perturbative QCD Odderon given at the lowest $\alpha_s$ order by the three
gluon exchange. Then we discuss the experimental indications for the Odderon
contribution to high energy proton-proton elastic scattering and some other
processes in which the Odderon may reveal itself.
