The Chandra Source Catalog (CSC) is the definitive catalog of X-ray sources detected by the Chandra X-ray Observatory. Version 2.0 (CSC2) is the second major release of the catalog; the current minor release is version 2.0.1, updated on 2020 November 24 (for more information see the Catalog Version History). CSC 2.0 represents a significant improvement with respect to version 1.1 in terms of sky coverage, sensitivity and capabilities. CSC2 includes measured properties for 317,167 unique compact and extended X-ray sources in the sky, allowing statistical analysis of large samples, as well as individual source studies. Extracted properties are provided for 928,280 individual observation detections identified in 10,382 Chandra ACIS and HRC-I imaging observations released publicly through the end of 2014. CSC 2.0 also includes—as an "alpha" release—photometric properties for 1,299 highly extended (≳30″) sources, together with surface brightness polygons for several contour levels. There are approximately 1,700 columns of tabular data with pertinent information about each source across 5 bands (broad, hard, medium, soft, and ultra-soft) for ACIS and 1 band (wide) for HRC (see the energy-bands page for the definition of these bands), and 40 data products per source.