  We report the first measurement of the X-ray spectrum of the z = 5.99 quasar
SDSSp J130608.26+035626.3 from a 120 ks observation by the Chandra ACIS-S
instrument. Between 0.5 and 7 keV, corresponding to 3.5--49 keV in the quasar
rest frame, we find an energy index of 0.86 +/- 0.2, consistent with the
typical indices found for radio quiet quasars at lower redshifts, and
inconsistent with the index required to match the diffuse X-ray background. We
have a weak indication of a redshifted Fe-K line. In comparing the counting
rate between an earlier, short observation and the longer observation reported
here, we find evidence for source variability at the 99.9% confidence level. We
note that other nearby X-ray sources would bias the measured alpha_{ox} = 1.70
by -0.09 if the X-ray flux were determined from within a 60" extraction circle.
Our results for the energy index and the alpha_{ox} are consistent with no
strong evolution in the active galactic nucleus emission mechanism with
redshift out to z ~ 6, and therefore with the picture that massive black holes
have already formed less than 1 Gyr after the big bang.
