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We report the discovery of a close quasar pair candidate at $z=5.66$,J2037--4537. J2037--4537 is resolved into two quasar images at the sameredshift in ground-based observations. Followup spectroscopy shows significantdifferences in both the continuum slopes and emission line properties of thetwo images. The two quasar images have a projected separation of $1\farcs24$($7.3\text{~kpc}$ at $z=5.66$) and a redshift difference of $\Deltaz\lesssim0.01$. High-resolution images taken by {\em Hubble Space Telescope} donot detect the foreground lensing galaxy. The observational features ofJ2037--4537 strongly disfavor the lensing hypothesis. If J2037--4537 is aphysical quasar pair, it indicates a quasar clustering signal of $\sim10^5$ ata separation of $\sim10$ proper kpc (pkpc), and gives the first observationalconstraint on the pair fraction of $z>5$ quasars,$f_\text{pair}(r<30\text{~pkpc})>0.3\%$. The properties of J2037--4537 areconsistent with those of merger-triggered quasar pairs in hydrodynamicalsimulations of galaxy mergers.

A Candidate Kiloparsec-scale Quasar Pair at $z=5.66$