We report the discovery of a quadruply imaged quasar, SDSS J125107.57+293540.5, selected from the Sloan Digital Sky Survey. Follow-up imaging reveals that the system consists of four blue pointlike components in a typical cusp lens geometry surrounding a central red galaxy. The source redshift is 0.802, and the lens redshift is 0.410. The maximum image separation between the lensed components is 1.79″. While the image configuration is well reproduced by standard mass models with reasonable parameter values, the flux ratios predicted by these models differ from the observed ratios in all bands. This is suggestive of small-scale structure in this lens, although a definitive identification of the anomaly requires more accurate photometry and astrometry.