The Sukhoi Su-57 (Russian: Сухой Су-57; unconfirmed NATO reporting name: Felon) is a stealth, single-seat, twin-engine multirole fifth-generation jet fighter being developed since 2002 for air superiority and attack operations. The aircraft is the product of the PAK FA, a fifth-generation fighter programme of the Russian Air Force. Sukhoi's internal name for the aircraft is T-50.

The fighter is designed to have supercruise, supermaneuverability, stealth, and advanced avionics to overcome the prior generation fighter aircraft as well as ground and naval defences. The Su-57 is intended to succeed the MiG-29 and Su-27 in the Russian Air Force.

The aircraft has a blended wing body fuselage and incorporates all-moving horizontal and vertical stabilizers. The aircraft incorporates thrust vectoring and has adjustable leading–edge vortex controllers (LEVCONs), and can provide trim and improve high angle of attack behaviour, including a quick stall recovery if the thrust vectoring system fails.

The aircraft canopy is made of composite material and 70-90 nm thick metal oxide layers with enhanced radar wave absorbing to minimize the radar return of the cockpit by 30% and protect the pilot from the impact of ultraviolet and thermal radiation. The Su-57's design emphasizes frontal stealth, with RCS-reducing features most apparent in the forward hemisphere; the shaping of the aft fuselage, the seams between parts, and rivets are much less optimized for radar stealth compared to the F-22.

Initial production batches of the Su-57 will use interim engines, a pair of NPO Saturn izdeliye 117, or AL-41F1 augmented turbofans. Closely related to the Saturn izdeliye 117S engine, or AL-41F1S used by the Su-35S, it is a highly improved and uprated variant of the AL-31 that powers the Su-27 family of aircraft. The AL-41F1 produces 93.1 kN of dry thrust, 147.1 kN of thrust in afterburner, and has a thrust to weight ratio of 10.5:1.

For air-to-air combat, the Su-57 is expected to carry four beyond-visual-range missiles in its two main weapons bays and two short-range missiles in the wing root weapons bays. The primary medium-range missile is the active radar-homing K-77M. The short-range missile is the infrared-homing K-74M2. A clean-sheet design short-range missile designated K-MD is being developed to eventually replace the K-74M2. Four large izdeliye 810 beyond-visual-range missiles can be carried, with two in each main weapons bay. Reportedly, the fighter will also be able to carry the long–range hypersonic R-37M missile.

The main avionics systems are the Sh-121 MIRES and the 101KS electro-optical system.
The Sh-121 consists of the N036 Byelka radar system and L402 Himalayas electronic countermeasures system. The N036 consists of the main nose-mounted N036-1-01 X band active electronically scanned array (AESA) radar, or active phased array radar, with 1,552 T/R modules and two side-looking N036B-1-01 X-band AESA radars with 358 T/R modules embedded in the cheeks of the forward fuselage for increased angular coverage.

According to Bill Sweetman, the Su-57's high operational speed and altitude combined with its standoff weaponry could be hinting at its role as a "sort of airborne sniper", designed to fly fast and high to engage enemy support aircraft. This claim is supported by Russia's intentions to adapt the new R-37M air-to-air missile with range of more than 300 km to the Su-57's armament, giving it a role similar to the MiG-31BM interceptors. Newly designed anti-ship weapons could also enable the Su-57 to perform as a maritime strike aircraft.