We report the discovery of near-sinusoidal radial velocity variations of the G0V star \rho CrB , with period 39.6 days and amplitude 67 m s ^ { -1 } .
These variations are consistent with the existence of an orbital companion in a circular orbit .
Adopting a mass of 1.0 M _ { \odot } for the primary , the companion has minimum mass about 1.1 Jupiter masses , and orbital radius about 0.23 AU .
Such an orbital radius is too large for tidal circularization of an initially eccentric orbit during the lifetime of the star , and hence we suggest that the low eccentricity is primordial , as would be expected for a planet formed in a dissipative circumstellar disk .