  We propose a new approach to test possible corrections to Newtonian gravity
using solar physics. The high accuracy of current solar models and new precise
observations allow one to constrain corrections to standard gravity at
unprecedented levels. Our case study is Eddington-inspired gravity, an
attractive modified theory of gravity which results in non-singular cosmology
and collapse. The theory is equivalent to standard gravity in vacuum, but it
sensibly differs from it within matter, for instance it affects the evolution
and the equilibrium structure of the Sun, giving different core temperature
profiles, deviations in the observed acoustic modes and in solar neutrino
fluxes. Comparing the predictions from a modified solar model with
observations, we constrain the coupling parameter of the theory, |kappa_g| <
3x10^5 m^5 s^2 / kg. Our results show that the Sun can be used to efficiently
constraint alternative theories of gravity.
