We report the discovery of a debris system associated with the similar to 30 Myr old G3/5V star HD 12039 using Spitzer Space Telescope observations from 3.6-160 mu m. An observed infrared excess (L-IR/L-* = 1 x 10(-4)) above the expected photosphere for lambda greater than or similar to 14 mu m is fit by thermally emitting material with a color temperature of T similar to 110 K, warmer than the majority of debris disks identified to date around Sun-like stars. The object is not detected at 70 mu m with a 3 sigma upper limit 6 times the expected photospheric flux. The spectrum of the infrared excess can be explained by warm, optically thin material comprised of blackbody-like grains of size greater than or similar to 7 mu m that reside in a belt orbiting the star at 4-6 AU. An alternate model dominated by smaller grains, near the blowout size a similar to 0.5 mu m, located at 30-40 AU is also possible but requires the dust to have been produced recently, since such small grains will be expelled from the system by radiation pressure in approximately a few times 10(2) yr.