X-ray absorption fine structure spectroscopy (XAFS) is a local probe, element-specific technique that provides the electronic nature and the local structure around the absorber atom. In this chapter, we present a brief introduction to XAFS technique, both in the near edge, X-ray absorption near-edge structure (XANES) and the extended X-ray absorption fine structure (EXAFS) region. Both regions contain complementary information. The XANES gives information on the electronic properties and the local geometry around the absorber atom, and the EXAFS provides the local structure parameters such as coordination numbers, distances, and disorder around the absorber atom. In particular, we focus on the potential of XAFS technique to the study of Fe oxides and oxyhydroxides, this technique being especially useful in nanoparticulate systems, even in very diluted conditions.