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We present the discoveries of WISEA J041451.67-585456.7 and WISEAJ181006.18-101000.5, two low-temperature (1200$-$1400 K), high proper motionT-type subdwarfs. Both objects were discovered via their high proper motion($>$0.5 arcsec yr$^{-1}$); WISEA J181006.18-101000.5 as part of the NEOWISEproper motion survey and WISEA J041451.67-585456.7 as part of the citizenscience project Backyard Worlds; Planet 9. We have confirmed both as browndwarfs with follow-up near-infrared spectroscopy. Their spectra andnear-infrared colors are unique amongst known brown dwarfs, with some colorsconsistent with L-type brown dwarfs and other colors resembling those of thelatest-type T dwarfs. While no forward model consistently reproduces thefeatures seen in their near-infrared spectra, the closest matches suggest verylow metallicities ([Fe/H] $\leq$ -1), making these objects likely the firstexamples of extreme subdwarfs of the T spectral class (esdT). WISEAJ041451.67-585456.7 and WISEA J181006.18-101000.5 are found to be part of asmall population of objects that occupy the "substellar transition zone," andhave the lowest masses and effective temperatures of all objects in this group.

WISEA J041451.67-585456.7 and WISEA J181006.18-101000.5: The First Extreme T-type Subdwarfs?