A computer operator is the person responsible for monitoring and controlling computer systems especially mainframe computer systems in a company or organization. Responsibilities include troubleshooting software and hardware problems, monitoring batch processing, maintaining and improving system performance and online availability, maintaining all system and application documentation, and assisting personnel with computer problems. Other responsibilities depend on the employer but might include system backups, maintaining computer room equipment including printers and tape storage devices, and providing customer support.

A computer operator may often be asked to know or learn the main computers' operating systems, such as IBM's OS/390 and its Job Entry Subsystem ( JES ), local area network operation, and applications used by an employer. A high school diploma is usually required. Most employers also require formal technical training or one to three years' experience. A computer operator must effectively interact and communicate with others, be able to work independently, have strong analytical skills, and be able to recognize and respond to problem situations.

A computer operator is a role in IT which oversees the running of computer systems, ensuring that the machines, and computers are running properly.The job of a computer operator as defined by the United States Bureau of Labor Statistics is to "monitor and control ... and respond to ... enter commands ... set controls on computer and peripheral devices. This Excludes Data Entry."

The position has evolved from its beginnings in the punched card era. A Bureau of Labor Statistics report published in 2018 showed that, in the public sector, a major employer of those categorized as Computer Operator was United States Postal Service. In the private sector, companies involved in data processing, hosting, or related services employed computer operators at an even higher rate. The states with the highest employment for computer operators, as of 2018, are: New York, Texas, California, New Jersey, and Florida.