F23 or F-23 may refer to:
- Fluorine-23 (23F), an isotope of fluorine
- Funk F-23, an American agricultural aircraft
- Getrag F23 transmission, an Italian 5-speed manual transmission
- Hirth F-23, an aircraft engine
- HMS Kanimbla (F23), a passenger ship requisitioned for the Royal Navy
- HMS Teazer (F23), a T-class destroyer of the Royal Navy
- Northrop YF-23, an American prototype fighter aircraft