In computer science, the number of concurrent users for a resource in a location, with the location being a computing network or a single computer, refers to the total number of people using the resource at the same time. The resource can, for example, be a computer program, a file, or the computer as a whole.

A computer operating system that allows several users to access a resource on the computer at the same time is a multiuser multitasking operating system, historically called a time-sharing operating system. The capacity of a system can also be measured in terms of maximum concurrent users, at which point system performance begins to degrade noticably.

Commercial vendors often license a software product by means of a concurrent users restriction. This allows a fixed number of users access to the product at a given time, and is in contrast with an unlimited use license.