  The solar chemical composition is an important ingredient in our
understanding of the formation, structure and evolution of both the Sun and our
solar system. Furthermore, it is an essential reference standard against which
the elemental contents of other astronomical objects are compared. In this
review we evaluate the current understanding of the solar photospheric
composition. In particular, we present a re-determination of the abundances of
nearly all available elements, using a realistic new 3-dimensional (3D),
time-dependent hydrodynamical model of the solar atmosphere. We have carefully
considered the atomic input data and selection of spectral lines, and accounted
for departures from LTE whenever possible. The end result is a comprehensive
and homogeneous compilation of the solar elemental abundances. Particularly
noteworthy findings are significantly lower abundances of carbon, nitrogen,
oxygen and neon compared with the widely-used values of a decade ago. The new
solar chemical composition is supported by a high degree of internal
consistency between available abundance indicators, and by agreement with
values obtained in the solar neighborhood and from the most pristine
meteorites. There is, however, a stark conflict with standard models of the
solar interior according to helioseismology, a discrepancy that has yet to find
a satisfactory resolution.
