We present the results of a 24 ks XMM-Newton observation of the NGC 5171 group of galaxies . NGC 5171 is unusual in that it is an X-ray bright group ( L _ { \mathrm { X } } > 10 ^ { 42 } \mbox { erg~ { } s } ^ { -1 } ) , with irregular contours which are not centred on a bright galaxy ( e.g . 13 ) . The global spectrum is adequately described by a single temperature APEC model with T _ { \mathrm { X } } = 0.96 \pm 0.04 keV , and Z = 0.13 \pm 0.02 \mathrm { Z _ { \odot } } , in good agreement with previous ROSAT data . We find the X-ray contours are centred on a bright ridge of emission stretching from the BGG to a nearby galaxy . Spectral mapping reveals this ridge to be both cool ( T _ { \mathrm { X } } \approx 1.1 keV ) and metallic ( Z \approx 0.4 \mathrm { Z _ { \odot } } ) in comparison to its surrounding , suggesting it is the result of a tidal interaction between the two galaxies . Optical data reveals the member galaxies to have a high velocity dispersion ( \sigma _ { \mathrm { v } } = 494 \pm 99 \mbox { km~ { } s } ^ { -1 } ) , and a significantly non-Gaussian velocity distribution , suggesting the group is in the process of merging . A region of hot gas with T _ { \mathrm { X } } = 1.58 \pm 0.36 keV is found to the West of the bright central ridge , and we interpret this as shock-heating resulting from the merging . A further region of emission to the South-East of the bright central ridge , with T _ { \mathrm { X } } = 1.14 \pm 0.13 keV , is probably associated with a background group , four times more distant .