The missing Xe(IV) oxide, XeO₂, has been synthesized at 0 °C by hydrolysis of XeF₄ in water and 2.00 M H₂SO_4(aq). Raman spectroscopy and ^16/18O isotopic enrichment studies indicate that XeO₂ possesses an extended structure in which Xe(IV) is oxygen bridged to four neighboring oxygen atoms to give a local square-planar XeO₄ geometry based on an AX₄E₂ valence shell electron pair repulsion (VSEPR) arrangement. The vibrational spectra of Xe¹⁶O₂ and Xe¹⁸O₂ amend prior vibrational assignments of xenon doped SiO₂ and are in accordance with prior speculation that xenon depletion from the Earth’s atmosphere may occur by xenon insertion at high temperatures and high pressures into SiO₂ in the Earth’s crust.