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We present very early UV to optical photometric and spectroscopicobservations of the peculiar Type IIn supernova (SN) 2011ht in UGC 5460. The UVobservations of the rise to peak are only the second ever recorded for a TypeIIn SN and are by far the most complete. The SN, first classified as a SNimpostor, slowly rose to a peak of M_V \sim -17 in \sim55 days. In contrast tothe \sim2 magnitude increase in the v-band light curve from the firstobservation until peak, the UV flux increased by >7 magnitudes. The opticalspectra are dominated by strong, Balmer emission with narrow peaks (FWHM\sim600km/s), very broad asymmetric wings (FWHM\sim4200 km/s), and blue shiftedabsorption (\sim300 km/s) superposed on a strong blue continuum. The UV spectraare dominated by FeII, MgII, SiII, and SiIII absorption lines broadened by\sim1500 km/s. Merged X-ray observations reveal aL_(0.2-10)=(1.0+/-0.2)x10^(39) erg/s. Some properties of SN 2011ht are similarto SN impostors, while others are comparable to Type IIn SNe. Early spectrashowed features typical of luminous blue variables at maximum and during gianteruptions. However, the broad emission profiles coupled with the strong UV fluxhave not been observed in previous SN impostors. The absolute magnitude andenergetics (~2.5x10^(49) ergs in the first 112 days) are reminiscent of normalType IIn SN, but the spectra are of a dense wind. We suggest that the mechanismfor creating this unusual profile could be a shock interacting with a shell ofmaterial that was ejected a year before the discovery of the SN.

The Unusual Temporal and Spectral Evolution of the Type IIn Supernova 2011ht