  We present the results of a spectroscopic campaign revealing that the
non-thermal radio emitter Cyg OB2 #8A is an O6 + O5.5 binary system. We propose
the very first orbital solution indicating a period of about 21.9 days. The
system appears to be eccentric (0.24 +/- 0.04) and is likely seen under a
rather low inclination angle. The mass ratio of the components is close to
unity. The impact of the binarity of this star in the framework of our
understanding of non-thermal radio emission from early-type stars is briefly
discussed.
