NASA’s Mars 2020 mission successfully landed the Perseverance rover in Jezero crater on February 18, 2021.This book provides the definitive pre-landing documentation of the Mars 2020 mission, its scientific payload elements, and its exploration area. The chapters in this volume include detailed descriptions of: The Perseverance mission, and its relationship to a possible Mars Sample Return campaign; The geology of the mission’s exploration environment in Jezero crater; and The purpose, design and operation of all seven instruments aboard the rover (Mastcam-Z, SHERLOC, RIMFAX,  Supercam, MOXIE, PIXL, and MEDA) as well as the engineering cameras and the Mars helicopter Ingenuity. NASA's ambitious Mars 2020 mission extends a long arc of Martian exploration by seeking evidence that life may once have existed on Mars, and by preparing a collection of samples for possible return to Earth by a future mission. Mars 2020 will also enable future exploration by characterizing modern weather conditions and by demonstrating new technologies. Previously published in Space Science Reviews in the Topical Collection "The Mars 2020 Mission"