The XVII International Feofilov Symposium on Spectroscopy of Crystals Doped with Rare Earth and Transition Metal Ions (IFS2018) continues a sequence of symposia organized by Petr P. Feofilov and started in Moscow in 1965. The first nine events were held as national meetings. For more than 20 years, symposia have been gathering researchers working in the fields of optical spectroscopy, condensed matter physics and solid state chemistry from all over the world. After the Xth (Saint Petersburg, 1995), XIth (Kazan, 2001), XIIth (Ekaterinburg, 2004), XIIIth (Lake Baikal, 2007), XIVth (St. Petersburg, 2010), XVth (Kazan, 2013) and XVIth (St. Petersburg, 2015) Symposia, IFS2018 will return once again in Ekaterinburg. Optical spectroscopy of crystalline and non-crystalline insulators and semiconductors doped with f- and d-ions; electron-phonon interactions and dynamics; relaxation of excited states; microwave-optical and terahertz spectroscopy; magnetic resonance spectroscopy; magneto-optical spectroscopy; cooperative processes and coherent phenomena; electron structure modeling and spectra simulation; crystal and ligand field theory; microscopic theory of exchange and hyperfine coupling; resonant inelastic X-ray scattering; nonlinear spectroscopy; probing of organic and biomaterials; charge transfer phenomena and charge ordering; solid-state lasers, scintillators, phosphors; crystallography aspects of optical materials development, and spectroscopy of photonic crystals belong to the main topics of plenary and keynote lectures, oral and poster presentations.