The Sukhoi Su-57 (T-50) was developed under the Perspektivniy Aviacionniy Complex Frontovoi Aviacii (Perspective Aviation Complex for Frontline Aviation) program to field a fifth generation multifunctional/multidimensional strike fighter for service with the Russia Federation Aerospace Forces from the third decade of the twenty first century. Taking to the air in January 2010, the T-50 prototype emerged from the LFI (Legikiy Frontovoi Istrebitel - Light Frontline Fighter) program that rose from the ashes of the cancelled Soviet era MFI (Mnogofunktsional'nyy Frontovoi Istrebitel - Multifunctional Frontline Fighter) program aimed at fielding a Sukhoi Su-27 heavy air superiority fighter replacement. This volume, which builds upon and advances the work conducted on the 2015 volume, covers the Su-57 program from conception of the MFI and LFI programs from the early 1980’s and 1990’s, to flight testing of the T-50 development and pre-series aircraft and initial service deliveries of series aircraft to the Russian Aerospace Forces in December 2020. The Su-57/T-50 design is described in detail, as are its various advanced systems, including low-observable technologies, power plant, radio-electronic, optoelectronics, electronic warfare, navigation and weapons etc. All technical information concenring the aircraft, systems and weapons comes from designer/developer/operator documentation. In regard to formal or informal writing, it has been deemed more appropriate to use the term 5th generation when referring to a specific aircraft design - Su-57 5th generation multifunctional fighter - and fifth generation when referring to overall programs - Russian fifth generation multifunctional fighter.