Top-quark production cross sections at higher perturbative orders

I present calculations of higher-order corrections to top-quark production via three different processes: the production of a top-antitop pair and a $Z$ boson; single-top quark production in the $s$-channel; and top-antitop production with a Higgs boson. It is shown that the contributions from soft-gluon corrections are numerically dominant and large in all these processes. I present approximate NNLO (aNNLO) and approximate N${}^3$LO (aN${}^3$LO) cross sections that include soft-gluon corrections added to the exact NLO QCD results. Electroweak corrections through NLO are also included for $t\bar{t}Z$ and $t\bar{t}H$ production. The theoretical predictions are compared to LHC measurements of total cross sections for these processes.