  We report the discovery of a new example of the rare class of highly
magnetized, rapidly rotating, helium enhanced, early B stars that produce
anomalously wide hydrogen emission due to a centrifugal magnetosphere (CM). The
star is Trumpler 16-26, a B1.5 V member of the Trumpler 16 open cluster. A CM
was initially suspected based on hydrogen Brackett series emission observed in
SDSS/APOGEE $H$-band spectra. Similar to the other stars of this type, the
emission was highly variable and at all times remarkable due to the extreme
velocity separations of the double peaks (up to 1300 km s$^{-1}$.) Another clue
lay in the TESS lightcurve, which shows two irregular eclipses per cycle when
phased with the likely 0.9718115 day rotation period, similar to the behavior
of the well known CM host star $\sigma$ Ori E. To confirm a strong magnetic
field and rotation-phase-locked variability, we initiated a follow-up campaign
consisting of optical spectropolarimetry and spectroscopy. The associated data
revealed a longitudinal magnetic field varying between $-3.1$ and $+1.6$ kG
with the period found from photometry. The optical spectra confirmed rapid
rotation ($v \sin i=195$ km s$^{-1}$), surface helium enhancement, and wide,
variable hydrogen emission. Tr16-26 is thus confirmed as the 20$^{\rm th}$
known, the fourth most rapidly rotating, and the faintest CM host star yet
discovered. With a projected dipole magnetic field strength of $B_{\rm d}>11$
kG, Tr16-26 is also among the most magnetic CM stars.
