  The discovery of the Higgs boson has opened a new avenue for exploring
physics beyond the Standard Model. In this review, we discuss cosmological
aspects of the simplest Higgs couplings to the hidden sector, known as the
Higgs portal. We focus on implications of such couplings for inflation, vacuum
stability and dark matter, with the latter including both the traditional
weakly interacting massive particles as well as feebly interacting scalars. The
cosmological impact of the Higgs portal can be important even for tiny values
of the couplings.
