  We present in analytic form the three-loop O(\alpha_s^2) correction to the H
-> gg partial width of the standard-model Higgs boson with intermediate mass
M_H << 2 M_t. Its knowledge is required because the O(\alpha_s) correction is
so sizeable that the theoretical prediction to this order is unlikely to be
reliable. For M_H=100 GeV, the resulting QCD correction factor reads
$1+(215/12)\alpha_s^{(5)}(M_H)/\pi+150.419 (\alpha_s^{(5)}(M_H)/\pi)^2 \approx
1+0.66+0.21$. The new three-loop correction increases the Higgs-boson hadronic
width by an amount of order 1%.
