The Large UV/Optical/Infrared (LUVOIR) Surveyor is a concept for a powerful general-purpose observatory spanning the far-UV to the near-infrared. Two variants are being studied: LUVOIR-A (15-m diameter primary mirror) and LUVOIR-B (8-m mirror). These powerful and flexible observatories will enable revolutionary new studies in astrophysics and planetary science. LUVOIR is being designed to take the next great leap in exoplanet studies, with direct images and spectra of rocky Earthsized exoplanets in the habitable zones of other stars. These data will allow a wide range of investigations, including analysis of terrestrial planet atmospheres, discovery of potentially habitable exoplanets, and searches for evidence of global biospheres. A key goal for LUVOIR is to conduct these studies on a set of candidate habitable exoplanets large enough to constrain the frequency of habitable conditions (dozens of rocky planets orbiting solar-type stars). LUVOIR will also provide revolutionary advances in a broad range of astrophysics — from the epoch of reionization, through galaxy formation and evolution, to star and planet formation. The observatory could also enable powerful remote sensing observations of Solar System bodies. The LUVOIR-A architecture offers up to 25 km resolution at Jupiter, enabling sensitive, high resolution observations over long time baselines and a broad wavelength range. Finally, perhaps LUVOIR's most important scientific capability is its ability to address not only the science questions of today, but those of the 2040s and beyond that we have not yet thought to ask.