  We report the discovery of a new Galactic candidate Luminous Blue Variable
(cLBV) via detection of an infrared circular nebula and follow-up spectroscopy
of its central star. The nebula, MN112, is one of many dozens of circular
nebulae detected at $24 \mu$m in the {\it Spitzer Space Telescope} archival
data, whose morphology is similar to that of nebulae associated with known
(c)LBVs and related evolved massive stars. Specifically, the core-halo
morphology of MN112 bears a striking resemblance to the circumstellar nebula
associated with the Galactic cLBV GAL 079.29+00.46, which suggests that both
nebulae might have a similar origin and that the central star of MN112 is a
LBV. The spectroscopy of the central star showed that its spectrum is almost
identical to that of the bona fide LBV P Cygni, which also supports the LBV
classification of the object. To further constrain the nature of MN112, we
searched for signatures of possible high-amplitude ($\ga 1$ mag) photometric
variability of the central star using archival and newly obtained photometric
data covering a 45 year period. We found that the B magnitude of the star was
constant ($\simeq$ 17.1$\pm$0.3 mag) over this period, while in the I band the
star brightened by $\simeq 0.4$ mag during the last 17 years. Although the
non-detection of large photometric variability leads us to use the prefix
`candidate' in the classification of MN112, we remind that the long-term
photometric stability is not unusual for genuine LBVs and that the brightness
of P Cygni remains relatively stable during the last three centuries.
