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