I report discovery of a new galaxy-scale gravitational lens system , identified using public data from the MaNGA survey , as part of a systematic search for lensed background line emitters . The lens is SDSS J170124.01+372258.0 , a giant elliptical galaxy with velocity dispersion \sigma = 256 km s ^ { -1 } , at a redshift of z _ { l } = 0.122 . After modelling and subtracting the target galaxy light , the integral-field data-cube reveals [ O ii ] , [ O iii ] and H \beta emission lines corresponding to a source at z _ { s } = 0.791 , forming an identifiable ring around the galaxy centre . If the ring is formed by a single lensed source , then the Einstein radius is R _ { Ein } \approx 2.3 arcsec , projecting to \sim 5 kpc at the distance of the lens . The total projected lensing mass is M _ { Ein } = ( 3.6 \pm 0.6 ) \times 10 ^ { 11 } M _ { \odot } , and the total J-band mass-to-light ratio is 3.0 \pm 0.7 solar units . Plausible estimates of the likely dark matter content could reconcile this with a Milky-Way-like initial mass function ( for which M / L \approx 1.5 is expected ) , but heavier IMFs are by no means excluded with the present data . An alternative interpretation of the system , with a more complex source plane , is also discussed . The discovery of this system bodes well for future lens searches based on MaNGA and other integral-field spectroscopic surveys .