  I present results for soft anomalous dimensions in single top-quark
production processes through three loops. I first discuss the cusp anomalous
dimension with one massive and one massless line at three loops. I then
calculate the three-loop soft anomalous dimension for $tW$ production and for
related processes with new physics such as $tZ$, $t\gamma$, and $tH^-$
production. This is followed by results at two and three loops for the soft
anomalous dimension matrix in $s$-channel single-top production and, finally,
in $t$-channel single-top production. These new results are needed for
soft-gluon resummation at N$^3$LL accuracy and for calculations of soft-gluon
corrections at N$^3$LO.
