F-X Project may refer to:
- F-X (Japan), Japan Air Self-Defense Force's next generation main combat aircraft procurement program.
- F-X fighter program, a multistage program to purchase modern aircraft for the Republic of Korea Air Force.
- Project F-X2 (known as F-X before 2007), a purchase of fighter aircraft by the Brazilian Air Force.
- A program by the United States Air Force that led to the McDonnell Douglas F-15 Eagle
- F-X (Turkey), known shortly as MMU in Turkey, a stealth twinjet all-weather air superiority fighter in development by the Turkish Aerospace Industries