  This article presents measurements of all three single top-quark production
channels. Detailed measurements of $t$-channel single top-quark production
using data collected by the ATLAS experiment in proton--proton collisions at a
centre-of-mass energy of 8 TeV are shown as well es first results using 13 TeV
at the LHC. The associated production of a top quark and a $W$ boson is
presented for data collected at 13 TeV, while the first evidence of single
top-quark production in the $s$-channel is shown for data collected at 8 TeV.
