  Measuring the Higgs couplings accurately at colliders is one of the best
routes for finding physics Beyond the Standard Model (BSM). If the measured
couplings deviate from the SM predictions, then this would give rise to
energy-growing processes that violate tree-level unitarity at some energy
scale, indicating new physics. In this paper, we extend previous work on
unitarity bounds from the Higgs potential and the Higgs couplings to vector
bosons, the top quark, $\gamma\gamma$ and $\gamma Z$; to the Higgs coupling to
gg. We show that the scale of new physics could be as low as $\sim 10$ TeV,
which although beyond the reach of the LHC, is well within the reach of the
future 100-TeV collider, and can also be probed indirectly in the High
Luminosity LHC (HL-LHC).
