We present the results of study of the Galactic candidate luminous blue variable Wray 15-906, revealed via detection of its infrared circumstellar shell (of approx2 pc in diameter) with the Wide-field Infrared Survey Explorer and the Herschel Space Observatory. Using the stellar atmosphere code CMFGEN and the Gaia parallax, we found that Wray 15-906 is a relatively low-luminosity, log(L/Lsun)approx5.4, star of temperature of 25pm2 kK, with a mass-loss rate of approx3times10^{-5} Msun/yr, a wind velocity of 280pm50 km/s, and a surface helium abundance of 65pm2 per cent (by mass). In the framework of single star evolution, the obtained results suggest that Wray 15-906 is a post-red supergiant star with initial mass of approx26pm2 Msun and that before exploding as a supernova it could transform for a short time into a WN11h star. Our spectroscopic monitoring with the Southern African Large Telescope (SALT) does not reveal significant changes in the spectrum of Wray 15-906 during the last 8 yr, while the V-band light curve of this star over years 1999--2019 shows quasi-periodic variability with a period of approx1700 d and an amplitude of approx0.1 mag. We estimated the mass of the shell to be 2.9pm0.5 Msun assuming the gas-to-dust mass ratio of 200. The presence of such a shell indicates that Wray 15-906 has suffered substantial mass loss in the recent past. We found that the open star cluster C1128-631 could be the birth place of Wray 15-906 provided that this star is a rejuvenated product of binary evolution (a blue straggler).
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