THE extragalactic radio source 3C273 was the first quasar to be identified1, and remains one of the nearest and most luminous quasars known. In radio images2-4, it appears as a bright, point-like nucleus from which emerges a single large jet; the jet is also apparent in optical images5-8, but the relatively poor resolution of ground-based optical data has hampered detailed comparisons with the radio maps. Here we present high-resolution intensity and polarization maps of the optical jet of 3C273 obtained using the Faint Object Camera on the Hubble Space Telescope. The optical emission is tightly confined to the core of the radio jet, and is resolved into a number of highly polarized knot structures. Both the optical and radio emission can be explained by synchrotron radiation from a stream of energetic particles burrowing into the surrounding medium. Comparison with the radio maps also reveals asymmetry in the emission across the jet, indicating significant lateral motion of the jet relative to the ambient medium. The onset of optical emission from the jet some distance from the nucleus of 3C273 could arise from the interaction of the jet with a shell of gaseous material surrounding the host galaxy.