1-9

1-9 may refer to:

• 0s, the first "decade" of the AD/CE time system (AD 1–9)
• 1% rule (Internet culture), also known as the 1–9–90 rule
• Two services of the New York City Subway which formerly ran together
  • 1 (New York City Subway service)
  • 9 (New York City Subway service)
• U.S. Route 1/9 concurrency in northern New Jersey
• Emergency telephone number for city police in Morocco