Volume 68 of Reviews in Mineralogy and Geochemistry reviews Oxygen in the Solar System, an element that is so critically important in so many ways to planetary science. The book is based on three open workshops: Oxygen in the Terrestrial Planets, held in Santa Fe, NM July 20-23, 2004; Oxygen in Asteroids and Meteorites, held in Flagstaff, AZ June 2-3, 2005; and Oxygen in Earliest Solar System Materials and Processes (and including the outer planets and comets), held in Gatlinburg, TN September 19-22, 2005. As a consequence of the cross-cutting approach, the final book spans a wide range of fields relating to oxygen, from the stellar nucleosynthesis of oxygen, to its occurrence in the interstellar medium, to the oxidation and isotopic record preserved in 4.56 Ga grains formed at the Solar System's birth, to its abundance and speciation in planets large and small, to its role in the petrologic and physical evolution of the terrestrial planets. Contents: Introduction Oxygen isotopes in the early Solar System - A historical perspective Abundance, notation, and fractionation of light stable isotopes Nucleosynthesis and chemical evolution of oxygen Oxygen in the interstellar medium Oxygen in the Sun Redox conditions in the solar nebula: observational, experimental, and theoretical constraints Oxygen isotopes of chondritic components Mass-independent oxygen isotope variation in the solar nebula Oxygen and other volatiles in the giant planets and their satellites Oxygen in comets and interplanetary dust particles Oxygen and asteroids Oxygen isotopes in asteroidal materials Oxygen isotopic composition and chemical correlations in meteorites and the terrestrial planets Record of low-temperature alteration in asteroids The oxygen cycle of the terrestrial planets: insights into the processing and history of oxygen in surface environments Redox conditions on small bodies, the Moon and Mars Terrestrial oxygen isotope variations and their implications for planetary lithospheres Basalts as probes of planetary interior redox state Rheological consequences of redox state