  Disformal theories of gravity are scalar-tensor theories where the scalar
couples derivatively to matter via the Jordan frame metric. These models have
recently attracted interest in the cosmological context since they admit
accelerating solutions. We derive the solution for a static isolated mass in
generic disformal gravity theories and transform it into the parameterised
post-Newtonian form. This allows us to investigate constraints placed on such
theories by local tests of gravity. The tightest constraints come from
preferred-frame effects due to the motion of the Solar System with respect to
the evolving cosmological background field. The constraints we obtain improve
upon the previous solar system constraints by two orders of magnitude, and
constrain the scale of the disformal coupling for generic models to
$\mathcal{M} \gtrsim 100$ eV. These constraints render all disformal effects
irrelevant for cosmology.
