"500 Person Sex" (５００人ＳＥＸ, EC-OPEN-0604) is a sex video released by Japanese adult video production house, Soft on Demand (SOD) on 4th May 2006. It is the largest known sex orgy recorded.

It features 250 couples, described by SOD as students, who enter what looks like a large warehouse, and over the course of two hours, engage in a variety of foreplay, mutual masturbation, and intercourse. All sexual acts are performed in near synchronization with all the other couples.

Unlike a typical orgy or swingers' party, each couple has sex only with themselves, and no other couple.

The 130 minute video, was produced by in-house production company SODcreate, and directed by Tsuchiya Yukitsugu (土屋幸嗣).

Video Source (including promotional pictures and screengrabs)