An edit conflict is a computer problem where multiple editors cannot all edit the same item during a short time period. The problem is encountered on wikis or distributed data systems. An edit conflict occurs when a shared document is being edited by more than one person at the same time, and the attempted changes are treated as incompatible with each other. One person attempts to edit the document, but upon trying to save the new version, another person has already modified the document in the intervening time period, thus causing a difference between the attempted edit and the already-made edit that must be resolved manually, and causing an "edit conflict" error message. According to computer writer Gary B. Shelly, "Many wikis will block the contributor who is attempting to edit the page from being able to do so until the contributor currently editing the page saves changes or remains idle on the page for an extended period of time."

The problem is common when working on heavily edited articles on Wikipedia, such as those about a "current event" or a "person suddenly in the news", or on other "high-traffic pages".