We present an exhaustive inventory of 40 r-process elements in a metal-poor r-process-enhanced ([Eu/Fe] = +1.3) star, HD 222925, which was likely enriched by a single r-process event. We obtained a high-resolution UV spectrum of the star using the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. The UV spectrum is rich with lines of r-process elements, complementing our previously-analyzed optical spectrum, and a preliminary analysis permits detection of numerous elements that are not otherwise detectable in ground-based optical spectra (including Ge, As, Se, Cd, Sb, Te, Ta, W, Re, Os, Ir, Pt, Au, Pb, and Bi). This abundance pattern represents the most complete r-process inventory observed beyond the Solar System, and the most complete r-process inventory produced in a single r-process event. This work is based on observations with the NASA/ESA Hubble Space Telescope obtained at STScI, which is operated by AURA, under NASA contract NAS 5-26555. Support for program HST-GO-15657 was provided through a grant from the STScI under NASA contract NAS 5-26555.