Exec may refer to:

• Exec, short for "executive officer"
• exec (operating system), an operating system function for running a program
• Exec (Amiga), the OS kernel of Amiga computers
• EXEC, an interpreted command procedure control language for IBM's VM/CMS operating system
• EXEC 2, an interpreted command procedure control language for IBM's VM/CMS operating system
• UNIVAC EXEC I, the original operating system developed for the UNIVAC 1107
• UNIVAC EXEC II, an operating system developed for the UNIVAC 1107
• UNIVAC EXEC 8, a.k.a. EXEC VIII, an operating system developed for the UNIVAC 1108
• A family of kit helicopters produced by RotorWay International

CMS EXEC, or EXEC, is an interpreted, command procedure control, computer programming language used by the CMS EXEC Processor supplied with the IBM Virtual Machine/Conversational Monitor System (VM/CMS) operating system.

The exec collection of functions of Unix-like operating systems cause the running process to be completely replaced by the program passed as an argument to the function. As a new process is not created, the process identifier (PID) does not change, but the data, heap and stack of the original process are replaced by those of the new process.