9-11 can refer to:

• The September 11, 2001 attacks
• A collection of interviews of Noam Chomsky by a variety of European publications and individual interviewers during the month after the September 11, 2001 attacks
• September 11 (month-day date notation)
• 9 November (day-month date notation)
• The North American universal emergency telephone number, 9-1-1. It was originally referred to as the "nine-eleven" service, but has long been exclusively called "nine-one-one" to emphasize the buttons pressed to activate it.

See also 911 (disambiguation)