  We have obtained FUV (904 -- 1187 \AA) spectra of U Gem in outburst with
FUSE. Three of the observations were acquired during the plateau phase of the
outburst, while the fourth was obtained during late outburst decline. The
plateau spectra have continuum shapes and fluxes that are approximated by
steady-state accretion disk model spectra with $\dot{m} \simeq$ 7e-09 M_sun/yr.
The spectra also show numerous absorption lines of H I, He II, and two- to
five-times ionized transitions of C, N, O, P, S and Si. There are no emission
features in the spectra, with the possible exception of a weak feature on the
red wing of the O VI doublet. The absorption lines are narrow (FWHM ~ 500
km/s), too narrow to arise from the disk photosphere, and at low velocities (<=
700 km/s). The S VI and O VI doublets are optically thick. The absorption lines
in the plateau spectra show orbital variability: in spectra obtained at orbital
phases 0.53 -- 0.79, low-ionization absorption lines appear and the central
depths of the pre-existing lines increase. The increase in line absorption
occurs at the same orbital phases as previously observed EUV and X-ray light
curve dips. If the absorbing material is in (near-) Keplerian rotation around
the disk, it must be located at large disk radii. The final observation
occurred when U Gem was about two magnitudes from optical quiescence. The
spectra are dominated by emission from an $\simeq$43,000 K, metal-enriched
white dwarf (WD). The inferred radius of the WD is 4.95e+08 cm, close to that
observed in quiescence. Allowing for a hot heated region on the surface of the
WD improves the fit to the spectrum at short (< 960 \AA) wavelengths.
