  Screened modified gravity theories evade the solar system tests that have
proved prohibitive for classical alternative gravity theories. In many cases,
they do not fit into the PPN formalism. The environmental dependence of the
screening has motivated a concerted effort to find new and novel probes of
gravity using objects that are well-studied but have hitherto not been used to
test gravity. Astrophysical objects---stars, galaxies, clusters---have proved
competitive tools for this purpose since they occupy the partially-screened
regime between solar system and the Hubble flow. In this article we review the
current astrophysical tests of screened modified gravity theories.
