On 2014 December 9.61, the All-sky Automated Survey for SuperNovae (ASAS-SN or "Assassin") discovered ASASSN-14lp just ~2 days after first light using a global array of 14cm diameter telescopes. ASASSN-14lp went on to become a bright supernova (V=11.94mag), second only to SN 2014J for the year. We present prediscovery photometry (with a detection less than a day after first light) and ultraviolet through near-infrared photometric and spectroscopic data covering the rise and fall of ASASSN-14lp for more than 100 days. We find that ASASSN-14lp had a broad light curve ({Delta}m_15_(B)=0.80+/-0.05), a B-band maximum at 2457015.82+/-0.03, a rise time of 16.94_-0.10_^+0.11^days, and moderate host-galaxy extinction (E(B-V)host=0.33+/-0.06). Using ASASSN-14lp, we derive a distance modulus for NGC 4666 of {mu}=30.8+/-0.2, corresponding to a distance of 14.7+/-1.5Mpc. However, adding ASASSN-14lp to the calibrating sample of Type Ia supernovae still requires an independent distance to the host galaxy. Finally, using our early-time photometric and spectroscopic observations, we rule out red giant secondaries and, assuming a favorable viewing angle and explosion time, any nondegenerate companion larger than 0.34R_{sun}_.