  We present the ultraviolet (UV) spectroscopic evolution of a tidal disruption
event (TDE) for the first time. After the discovery of the nearby TDE
iPTF16fnl, we obtained a series of observations with the Space Telescope
Imaging Spectrograph (STIS) onboard the Hubble Space Telescope (HST). The
dominant emission features closely resemble those seen in the UV spectra of the
TDE ASASSN-14li and are also similar to those of N-rich quasars. However, there
is significant evolution in the shape and central wavelength of the line
profiles over the course of our observations, such that at early times the
lines are broad and redshifted, while at later times the lines are
significantly narrower and peak near the wavelengths of their corresponding
atomic transitions. Like ASASSN-14li, but unlike N-rich quasars, iPTF16fnl
shows neither MgII$\lambda 2798$\AA\ nor CIII]$\lambda 1909$\AA\ emission
features. We also present optical photometry and spectroscopy, which suggest
that the complex HeII profiles observed in the optical spectra of many TDEs are
in part due to the presence of NIII and CIII Wolf-Rayet features, which can
potentially serve as probes of the far-UV when space-based observations are not
possible. Finally, we use Swift XRT and UVOT observations to place strong
limits on the X-ray emission and determine the characteristic temperature,
radius, and luminosity of the emitting material. We find that iPTF16fnl is
subluminous and evolves more rapidly than other optically discovered TDEs.
