  We report an observation of ultra-high energy (UHE) gamma rays from the
Galactic Center region, using seven years of data collected by the
High-Altitude Water Cherenkov (HAWC) Observatory. The HAWC data are best
described as a point-like source (HAWC J1746-2856) with a power-law spectrum
($\mathrm{d}N/\mathrm{d}E=\phi(E/26 \,\text{TeV})^{\gamma}$), where
$\gamma=-2.88 \pm 0.15_{\text{stat}} - 0.1_{\text{sys}} $ and $\phi=1.5 \times
10^{-15}$ (TeV cm$^{2}$s)$^{-1}$ $\pm\,
0.3_{\text{stat}}\,^{+0.08_{\text{sys}}}_{-0.13_{\text{sys}}}$ extending from 6
to 114 TeV. We find no evidence of a spectral cutoff up to $100$ TeV using HAWC
data. Two known point-like gamma-ray sources are spatially coincident with the
HAWC gamma-ray excess: Sgr A$^{*}$ (HESS J1745-290) and the Arc (HESS
J1746-285). We subtract the known flux contribution of these point sources from
the measured flux of HAWC J1746-2856 to exclude their contamination and show
that the excess observed by HAWC remains significant ($>$5$\sigma$) with the
spectrum extending to $>$100 TeV. Our result supports that these detected UHE
gamma rays can originate via hadronic interaction of PeV cosmic-ray protons
with the dense ambient gas and confirms the presence of a proton PeVatron at
the Galactic Center.
