109 may refer to:
- 109 (number), the integer following 108 and preceding 110
- AD 109, a year of the Julian calendar, in the second century AD
- 109 BC, a year of the pre-Julian Roman calendar
- 109 (department store), a department store in Shibuya, Tokyo, Japan
- 109 (MBTA bus), a bus route in Boston, Massachusetts, USA
- Messerschmitt Bf 109, a German World War II fighter plane
- 109 Felicitas, a main-belt asteroid