Eternal September or the September that never ended was a cultural phenomenon during a period beginning around late 1993 and early 1994, when Internet service providers began offering Usenet access to many new users.[1][2] Prior to this, the only sudden changes in the volume of new users of Usenet occurred each September, when cohorts of university students would gain access to it for the first time, in sync with the academic calendar.

The flood of new and generally inexperienced Internet users directed to Usenet by commercial ISPs in 1993 and subsequent years swamped the existing culture of those forums and their ability to self-moderate and enforce existing norms.