The X-ray Surveyor mission concept is designed to make dramatic increases in discovery space and science capabilities for X-ray astronomy. These would be accomplished through orders of magnitude improvements over Chandra in sensitivity, field of view for sub-arcsec imaging, effective area for grating spectroscopy, and by providing high spectral resolution capabilities for extended objects on 1-arcsec angular scales. An X-ray observatory with such capabilities, operating in concert with other major astronomical facilities of the 2020-2030s, is required to address and solve some of the greatest challenges in modern astrophysics. The X-ray Surveyor will shed light on the formation of supermassive black holes by being able to detect X-rays from these objects as they grow beyond their seed state in the first galaxies. Direct data on the nature and operating modes of feedback will be provided by characterizing hot gas in galaxies and groups on scales from the very near vicinity of the central black out to the virial radius. A new era in our understanding of the plasma physics effects on astrophysical scales will be opened, for example, by resolving the detailed structure of relativistic shocks in pulsar wind nebulae and the gas turbulence in galaxy clusters. The detailed structure of the Cosmic Web will be exposed for the first time by mapping X-ray emission from hot gas in its filaments. The outstanding capabilities of X-ray Surveyor will make it an indispensable research tool in nearly every area of astrophysics.