Measurements of single-top-quark production in proton-proton collisions are presented based on the 8 TeV and 13 TeV ATLAS datasets. The recent combination of the ATLAS and CMS Run 1 single-top-quark measurements is discussed. This combination leads to the most precise direct measurement of the CKM-matrix element Vtb. An interesting quantum effect is the interference of tW and top-quark-pair production which is studied in a dedicated analysis. Differential cross-sections of the tW process have also been measured. The large Run 2 data set gives also access to rare single-top-quark processes, such as tZ production. The latest results on this production mode will be reviewed.