  One of the central concepts in modern theoretical physics, gauge symmetry, is
typically realised by lifting a finite-dimensional global symmetry group of a
given functional to an infinite-dimensional local one by extending the
functional to include gauge fields. In this contribution we review the
construction of gauged actions for two-dimensional sigma models, considering a
more general notion to be gauged, namely that of a (possibly singular)
foliation. In particular, the original action does not need to have any global
symmetry for this purpose. Moreover, reformulating the ungauged theory by means
of auxiliary 1-form fields taking values in the generalised tangent bundle over
the target, all possible such gauge theories result from restriction of these
fields to take values in (possibly small) Dirac structures. This turns all the
remaining 1-form fields into gauge fields and leads to the presence of a local
symmetry. We recall all needed mathematical notions, those of (higher) Lie
algebroids, Courant algebroids, and Dirac structures.
