Westerlund 1-243 or Wd 1-243 is a luminous blue variable (LBV) star undergoing an eruptive phase located within the outskirts of the super star cluster Westerlund 1.

[6] Located about 13,400 ly (4,100 pc) from Earth,[5] it has a luminosity of 0.73 million L☉ making it one of the most luminous stars known.

Many lines are complex emission/absorption blends, with significant spectral evolution occurring on timescales of just a few days.

[3] Westerlund 1-243 has a temperature of ~8,500 K determined from modelling the absorption line spectrum.

The K-band spectrum also implies a higher temperature than that of a typical yellow hypergiant and suggests that Westerlund 1-243 may be evolving back towards a hotter state.