  All known interacting 6D superconformal field theories (SCFTs) have a tensor
branch which includes anti-chiral two-forms and a corresponding lattice of
string charges. Automorphisms of this lattice preserve the Dirac pairing and
specify discrete global and gauge symmetries of the 6D theory. In this paper we
compute this automorphism group for 6D SCFTs. This discrete data determines the
geometric structure of the moduli space of vacua. Upon compactification, these
automorphisms generate Seiberg-like dualities, as well as additional theories
in discrete quotients by the 6D global symmetries. When a perturbative
realization is available, these discrete quotients correspond to including
additional orientifold planes in the string construction.
