We report on the detection of deuterated molecular hydrogen , HD , at z = 0.18 . HD and H _ { 2 } are detected in HST/COS data of a low metallicity ( Z \sim 0.07 Z _ { \odot } ) damped Ly \alpha system at z = 0.18562 toward QSO B 0120 - 28 , with log N ( H I ) = 20.50 \pm 0.10 . Four absorption components are clearly resolved in H _ { 2 } while two components are resolved in HD ; the bulk of the molecular hydrogen is associated with the components traced by HD . We find total column densities log N ( HD ) = 14.82 \pm 0.15 and log N ( H _ { 2 } ) = 20.00 \pm 0.10 . This system has a high molecular fraction , f ( H _ { 2 } ) = 0.39 \pm 0.10 and a low HD to H _ { 2 } ratio , log ( HD/2H _ { 2 } ) = -5.5 \pm 0.2 dex . The excitation temperature , T _ { 01 } = 65 \pm 2 K , in the component containing the bulk of the molecular gas is lower than in other DLAs . These properties are unlike those in other higher redshift DLA systems known to contain HD , but are consistent with what is observed in dense clouds in the Milky Way .