  The total and differential Higgs boson production cross-sections are measured
through a combined statistical analysis of the $H \rightarrow ZZ^* \rightarrow
4\ell$ and $H \rightarrow \gamma \gamma$ decay channels. The results are based
on a dataset of 139 fb$^{-1}$ of proton-proton collisions at a centre-of-mass
energy of 13 TeV, recorded by the ATLAS detector at the Large Hadron Collider.
The measured total Higgs boson production cross-section is 55.5$^{+4.0}_{-3.8}$
pb, consistent with the Standard Model prediction of 55.6$\pm$ 2.5 pb. All
results from the two decay channels are compatible with each other, and their
combination agrees with the Standard Model predictions. A combined statistical
interpretation of the measured fiducial cross-sections as a function of the
Higgs boson transverse momentum is performed in order to probe the Yukawa
couplings to the bottom and charm quarks. A similar interpretation is performed
by including also the constraints from the measurements of Higgs boson
production in association with a $W$ or $Z$ boson in the $H \rightarrow
b\bar{b}$ and $c\bar{c}$ decay channels.
