Number nine may refer to:
- 9 (number), natural number
- Number Nine, Arkansas, a community in the United States
- Number Nine (album) by Chris Hülsbeck
- Number 9 Audio Group, a recording studio located in Toronto, Ontario, Canada
- Number Nine Visual Technology, a computer hardware manufacturer whose primary business was video cards
- New Mexico No. 9, or No. 9, a chile pepper cultivar
- #9, the flagship beer of Magic Hat Brewing Company
- Number nine, repeated phrase on the Beatles recorded composition Revolution 9
- Number 9, a song by Korean Girl Group T-ara on their EP Again
- Number (N)ine, a Japanese fashion brand found in Tokyo in 1996
- Number Nine, assistant to Jenny Jump in the Oz books by John R. Neill
- Number 9, the shirt number often worn by an association football team's centre forward
- False 9 or False Number 9, a term used to describe an unconventional association football lone striker or centre-forward, who drops deep into midfield