The KAI KF-21 Boramae (Korean: KF-21 보라매; KF-21 Fighting Hawk; formerly known as KF-X) is a South Korean-led fighter aircraft development program with the initial goal of producing multirole fighters for the Republic of Korea Air Force (ROKAF). The airframe uses stealth technology but carries weapons externally, and features such as internal bays will be introduced later with KF-21EX program. The KAI KF-X is South Korea's second domestic fighter jet development program, following the FA-50.

The program is led by the South Korean government, which holds 60% of the program's shares. Indonesia took a 20% stake in the program in 2010 and participates in the program through Indonesian Aerospace since the start of KF-21 development in 2011, and the remaining 20% is held by private partners including the manufacturer Korea Aerospace Industries (KAI). Later, in August 2024, Indonesia's stake was reduced to 7.5% or 409 million USD when the head of the program, the Defense Acquisition Program Administration (DAPA), cut Indonesia's development contribution due to Indonesian government request.

In April 2021, the first prototype was completed and unveiled during a rollout ceremony at the headquarters of KAI at Sacheon Airport. It was named the Boramae. The first test flight was on 19 July 2022, with manufacturing scheduled to begin in 2026. At least 40 aircraft are planned to be delivered by 2028, with South Korea expecting to deploy 120 of the aircraft by 2032. It will also be available for export. The Republic of Korea Air Force will begin replacing its F-4D/E Phantom II and F-5E/F Tiger II jets with KF-21s. Later, F-16 Fighting Falcon and F-15EX Eagle IIs will also be replaced.