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We report the discovery of a gravitationally lensed quasar identifiedserendipitously in the Sloan Digital Sky Survey (SDSS). The object, SDSSJ094604.90+183541.8, was initially targeted for spectroscopy as a luminous redgalaxy, but the SDSS spectrum has the features of both a z=0.388 galaxy and az=4.8 quasar. We have obtained additional imaging that resolves the system intotwo quasar images separated by 3.06 arcsec and a bright galaxy that is stronglyblended with one of the quasar images. We confirm spectroscopically that thetwo quasar images represent a single lensed source at z=4.8 with a totalmagnification of 3.2, and we derive a model for the lensing galaxy. This is thehighest redshift lensed quasar currently known. We examine the issuessurrounding the selection of such an unusual object from existing data andbriefly discuss implications for lensed quasar surveys.

SDSS J094604.90+183541.8: A Gravitationally Lensed Quasar at z=4.8