Discovery of a color-selected quasar at z=5.50

We present observations of RD J030117+002025, a quasar at z = 5.50 discover ed from deep, multicolor, ground-based observations covering 74 arcmin(2). This is the most distant quasar or active galaxy currently known. The objec t was targeted as an R-band dropout, with R-AB > 26.3 (3 sigma limit in a 3 " diameter region), I-AB = 23.8, and z(AB) = 23.4. The Kecknow-Resolution Imaging Spectrometer spectrum shows broad Ly alpha/N v lambda 1240 emission and sharp absorption decrements from the highly redshifted hydrogen forest s. The fractional continuum depression due to the Ly alpha forest is D-A = 0.90. RD J030117+002025 is the least luminous high-redshift quasar known (M -B approximate to -22.7).