  We report on the detection by Swift of GRB 080913, and subsequent
optical/near-infrared follow-up observations by GROND which led to the
discovery of its optical/NIR afterglow and the recognition of its high-z nature
via the detection of a spectral break between the i' and z' bands. Spectroscopy
obtained at the ESO-VLT revealed a continuum extending down to lambda = 9400 A,
and zero flux for 7500 A < lambda<9400 A, which we interpret as the onset of a
Gunn-Peterson trough at z=6.695+-0.025 (95.5% conf. level), making GRB 080913
the highest redshift GRB to date, and more distant than the highest-redshift
QSO. We note that many redshift indicators which are based on promptly
available burst or afterglow properties have failed for GRB 080913. We report
on our follow-up campaign and compare the properties of GRB 080913 with bursts
at lower redshift. In particular, since the afterglow of this burst is fainter
than typical for GRBs, we show that 2m-class telescopes can identify most
high-redshift GRBs.
