In this Letter we report the detection of a strong and extremely blueshifted X-ray absorption feature in the 1 Ms Chandra spectrum of CXOCDFS J033260.0-274748, a quasar at z=2.579 with L2-10keV~4×1044 ergs s-1. The broad absorption feature at ~6.3 keV in the observed frame can be fitted either as an absorption edge at 20.9 keV or as a broad absorption line at 22.2 keV rest frame. The absorber has to be extremely ionized with an ionization parameter ξ~104, and a high column density, NH>5×1023 cm-2. We reject the possibility of a statistical or instrumental artifact. The most likely interpretation is an extremely blueshifted broad absorption line or absorption edge, due to H or He-like iron in a relativistic jetlike outflow with bulk velocity of ~0.7c-0.8c. Similar relativistic outflows have been reported in the X-ray spectra of several other AGNs in the past few years.