We present observations and interpretation of the Type IIn supernova SN 2008am discovered by the ROTSE Supernova Verification Project (RSVP). SN 2008am peaked at approximately -22.3mag at a redshift of z=0.2338, giving it a peak luminosity of ~3x10^44^erg/s and making it one of the most luminous supernovae ever observed. The host galaxy appears to be an SB1 of normal luminosity (M_r'~-20) with metallicity Z~0.4Z{sun}_. ROTSE upper limits and detections constrain the rise time to be ~34 days in the rest frame, significantly shorter than similar events, SN 2006gy and SN 2006tf. Photometric observations in the ultraviolet, optical, and infrared bands (J, H, Ks) constrain the spectral energy distribution evolution. We obtained six optical spectra of the supernova, five on the early decline from maximum light and a sixth nearly a year later plus a very late time spectrum (~2yr) of the host galaxy. The spectra of SN 2008am show strong Balmer-line and HeI5876 emission with intermediate widths (~25{AA}) in the first ~40 days after optical maximum.